feat(series): land on the current episode, not season 1 (UR-062, UR-063, UR-064)

Opening a series dumped the viewer at the top of season 1, and its Play
button played nothing at all: it resolved `$libraryItems[0]` — the first
*season* by SortName — and navigated to `/player/<seasonId>`, which the
player route bounced straight back to `/library/<seasonId>`.

The backend could already answer "where is this viewer in this show":
`repository_get_next_up_episodes` has accepted a `series_id` since it was
written and no caller had ever passed one.

Backend (DR-101, DR-106)
- `repository/series_progress.rs`: `pick_current_episode` — in progress,
  else Next Up, else first unwatched, else the premiere. The third rung is
  the offline path, where Next Up is always empty. `sort_series_order` puts
  specials (season 0) after the numbered seasons.
- `repository_get_series_episodes` takes over the season fan-out and the
  flat-series fallback, which were domain knowledge living in the frontend.
- `clear_watch_history` maps to Jellyfin's mark-unplayed (recursive over a
  container, also zeroes resume). Offline it refuses rather than diverging
  state the next sync would undo.

Frontend (DR-102, DR-103, DR-104, DR-107)
- Seasons collapse; only the current one is expanded, and the current
  episode is badged and scrolled into view.
- Hero button reads `Resume S2E4` / `Play S1E1` and opens that episode's
  focus view, where Play commits (ux-flows §5B.5).
- Seasons are no longer a destination: `/library/<seasonId>` redirects to
  `/library/<seriesId>#season-N`, and every inbound link follows.
- The "More Episodes" strip spans the whole series, so a season finale
  offers the next premiere instead of dead-ending (§5B.2).
- Clear-history buttons on the series hero and each season header.

Routes (DR-105)
- `/library/tv` and `/library/movies` absorb their all-titles and genres
  pages as `?view=` tabs; the four legacy routes redirect. 6 video routes
  become 2, and `/library/shows/genres` stops being the odd one out.

Logic extracted to `seriesNavigation.ts`, `episodeStrip.ts` and
`libraryView.ts` so it is unit-tested rather than buried in components.
Spec: docs/specs/series-current-episode-navigation.md

src/routes/library/[id]/+page.svelte

@@ -1,4 +1,4 @@
-<!-- TRACES: UR-035, UR-038, UR-048 | DR-043, DR-062 -->
+<!-- TRACES: UR-035, UR-038, UR-048, UR-062 | DR-043, DR-062, DR-102, DR-103 -->
 <script lang="ts">
   import { onMount, untrack } from "svelte";
   import { page } from "$app/stores";
@@ -17,6 +17,7 @@
   import SeasonSection from "$lib/components/library/SeasonSection.svelte";
   import EpisodeFocusView from "$lib/components/library/EpisodeFocusView.svelte";
   import SeriesDownloadButton from "$lib/components/library/SeriesDownloadButton.svelte";
+  import ClearHistoryButton from "$lib/components/library/ClearHistoryButton.svelte";
   import VideoDownloadButton from "$lib/components/library/VideoDownloadButton.svelte";
   import CastSection from "$lib/components/library/CastSection.svelte";
   import PersonDetailView from "$lib/components/library/PersonDetailView.svelte";
@@ -28,17 +29,27 @@
   import CachedImage from "$lib/components/common/CachedImage.svelte";
   import BackButton from "$lib/components/common/BackButton.svelte";
   import ArtistLinks from "$lib/components/library/ArtistLinks.svelte";
-
-  interface SeasonData {
-    season: MediaItem;
-    episodes: MediaItem[];
-  }
+  import {
+    groupEpisodesBySeason,
+    seasonAnchorId,
+    seasonRedirectTarget,
+    episodeFocusHref,
+    seriesPlayHref,
+    seriesPlayLabel,
+    initialExpandedSeasons,
+    type SeasonData,
+  } from "$lib/components/library/seriesNavigation";
 
   let item = $state<MediaItem | null>(null);
   let loading = $state(true);
   let error = $state<string | null>(null);
   let seasonData = $state<SeasonData[]>([]);
   let directFetchedEpisode = $state<MediaItem | null>(null);
+  // The episode the viewer is up to. Resolved by Rust (DR-101), not here.
+  let currentEpisode = $state<MediaItem | null>(null);
+  // Season ids whose episode list is open. A reading position, not a saved
+  // preference, so it resets with each load (DR-107).
+  let expandedSeasons = $state<Set<string>>(new Set());
 
   // Track if we've done an initial load and previous server state
   let hasLoadedOnce = false;
@@ -81,10 +92,25 @@
       error = null;
       seasonData = [];
       directFetchedEpisode = null;
+      currentEpisode = null;
+      expandedSeasons = new Set();
     }
 
     try {
       item = await library.loadItem(itemId);
+
+      // A season is not a destination — send it to its series, anchored at that
+      // season, so the episodes of every season stay one continuous list.
+      // TRACES: UR-062 | DR-103
+      if (item?.kind === "season") {
+        const target = seasonRedirectTarget(item);
+        if (target) {
+          await goto(target, { replaceState: true });
+          return;
+        }
+        // No seriesId (stale cache / deep link) — fall through to the generic
+        // rendering below rather than stranding the user.
+      }
       console.log(`[LibraryDetail] ✓ Loaded item: ${item?.name} (${item?.kind})`);
       console.log(`[LibraryDetail] - Has people? ${item?.people ? `YES (${item.people.length})` : 'NO'}`);
       if (item?.people) {
@@ -129,64 +155,42 @@
         }
       }
 
-      // For Series, load seasons and their episodes
+      // For Series, load every episode across all seasons plus the episode the
+      // viewer is up to. Both come from Rust: the season fan-out (and the
+      // flat-series fallback for shows whose children are episodes rather than
+      // season folders) is Jellyfin's shape, and "which episode is current" is
+      // domain policy — neither belongs in the presentation layer.
+      // TRACES: UR-062 | DR-101, DR-102
       if (item?.kind === "series") {
-        const seasons = $libraryItems.filter((i) => i.kind === "season");
         const repo = auth.getRepository();
+        const seasons = $libraryItems.filter((i) => i.kind === "season");
 
-        // Load episodes for each season in parallel
-        const seasonDataPromises = seasons.map(async (season) => {
-          const result = await repo.getItems(season.id, { limit: 100 });
-          const episodes = result.items
-            .filter((i) => i.kind === "episode")
-            .sort((a, b) => (a.indexNumber || 0) - (b.indexNumber || 0));
-          return { season, episodes };
-        });
+        const [episodes, current] = await Promise.all([
+          repo.getSeriesEpisodes(itemId),
+          // Best-effort: a series still renders if the anchor cannot be resolved.
+          repo.getSeriesCurrentEpisode(itemId).catch((e) => {
+            console.warn("Could not resolve the current episode:", e);
+            return null;
+          }),
+        ]);
 
-        seasonData = await Promise.all(seasonDataPromises);
-        // Sort seasons by index number
-        seasonData.sort((a, b) => (a.season.indexNumber || 0) - (b.season.indexNumber || 0));
-
-        // Some series expose episodes directly as children rather than under
-        // season folders. In that case the season fetch above yields nothing —
-        // group the flat episode children by their season number so the Episode
-        // Focus View still has a populated `allEpisodes` (otherwise "More
-        // Episodes" collapses to just the current episode).
-        if (seasonData.every((s) => s.episodes.length === 0)) {
-          const flatEpisodes = $libraryItems.filter((i) => i.kind === "episode");
-          if (flatEpisodes.length > 0) {
-            const bySeason = new Map<number, MediaItem[]>();
-            for (const ep of flatEpisodes) {
-              const key = ep.parentIndexNumber ?? 1;
-              (bySeason.get(key) ?? bySeason.set(key, []).get(key)!).push(ep);
-            }
-            seasonData = [...bySeason.entries()]
-              .sort(([a], [b]) => a - b)
-              .map(([seasonNumber, episodes]) => ({
-                // Synthesize a minimal season header from the episodes we have.
-                season: {
-                  ...(seasons.find((s) => s.indexNumber === seasonNumber) ?? episodes[0]),
-                  kind: "season",
-                  indexNumber: seasonNumber,
-                  name: `Season ${seasonNumber}`,
-                } as MediaItem,
-                episodes: episodes.sort((a, b) => (a.indexNumber || 0) - (b.indexNumber || 0)),
-              }));
-          }
-        }
+        seasonData = groupEpisodesBySeason(seasons, episodes);
+        currentEpisode = current;
+        // Open only the season the viewer is in (DR-107).
+        expandedSeasons = initialExpandedSeasons(
+          seasonData,
+          current?.id,
+          $page.url.searchParams.get("episode")
+        );
 
         // If we have a focused episode ID but couldn't find it in the seasons,
         // fetch it directly (handles ID mismatch between APIs)
         const episodeIdParam = $page.url.searchParams.get("episode");
-        if (episodeIdParam) {
-          const allEps = seasonData.flatMap((s) => s.episodes);
-          const foundInSeasons = allEps.some((e) => e.id === episodeIdParam);
-          if (!foundInSeasons) {
-            try {
-              directFetchedEpisode = await repo.getItem(episodeIdParam);
-            } catch {
-              console.warn("Could not fetch focused episode directly:", episodeIdParam);
-            }
+        if (episodeIdParam && !episodes.some((e) => e.id === episodeIdParam)) {
+          try {
+            directFetchedEpisode = await repo.getItem(episodeIdParam);
+          } catch {
+            console.warn("Could not fetch focused episode directly:", episodeIdParam);
           }
         }
       }
@@ -224,14 +228,21 @@
       return;
     }
     switch (clickedItem.kind) {
-      case "series":
+      // A season link lands on its series, anchored at that season — seasons
+      // have no page of their own (DR-103).
       case "season":
+        goto(seasonRedirectTarget(clickedItem) ?? `/library/${clickedItem.id}`);
+        break;
+      // An episode always opens in the context of its series (ux-flows §5B.1).
+      case "episode":
+        goto(episodeFocusHref(clickedItem));
+        break;
+      case "series":
       case "album":
       case "artist":
       case "folder":
       case "playlist":
       case "channel":
-      case "episode":
       case "movie":
         goto(`/library/${clickedItem.id}`);
         break;
@@ -244,15 +255,29 @@
   // Removed custom handleTrackClick - let TrackList use its built-in playback logic
   // This fixes Android playback issues where navigation-based approach was hanging
 
+  function toggleSeason(seasonId: string) {
+    // Reassign rather than mutate — a Set mutation is invisible to $state.
+    const next = new Set(expandedSeasons);
+    if (!next.delete(seasonId)) next.add(seasonId);
+    expandedSeasons = next;
+  }
+
   function handleEpisodeClick(episode: MediaItem) {
-    // Play the episode with the series queued for next episode
-    goto(`/player/${episode.id}`);
+    // Swap focus to the episode in place; playback starts from the focus view's
+    // own Play button, never from a list tap (ux-flows §5B.1, §5B.5).
+    goto(episodeFocusHref(episode));
   }
 
   async function handlePlayAll() {
     // For single items (Episode, Movie), play the item directly
     if (item?.kind === "episode" || item?.kind === "movie") {
       goto(`/player/${itemId}`);
+    } else if (item?.kind === "series" && itemId) {
+      // Open the episode the viewer is up to, where an explicit Play/Resume
+      // commits. Play on a container navigates; Play on a leaf plays.
+      // TRACES: UR-062 | DR-102
+      const target = seriesPlayHref(itemId, currentEpisode);
+      if (target) goto(target);
     } else if (item?.kind === "album" && $libraryItems.length > 0) {
       // For albums, use the backend command (backend fetches and queues all tracks)
       try {
@@ -293,6 +318,11 @@
         console.error("Failed to shuffle play album:", e);
         alert(`Failed to shuffle play: ${e instanceof Error ? e.message : 'Unknown error'}`);
       }
+    } else if (item?.kind === "series" && allEpisodes.length > 0) {
+      // Shuffle a *series* means a random episode, not a random season — the
+      // player has nothing to do with a season id.
+      const random = allEpisodes[Math.floor(Math.random() * allEpisodes.length)];
+      goto(`/player/${random.id}?restart=true`);
     } else if ($libraryItems.length > 0) {
       const randomIndex = Math.floor(Math.random() * $libraryItems.length);
       goto(`/player/${$libraryItems[randomIndex].id}?queue=parent:${itemId}&shuffle=true`);
@@ -304,6 +334,10 @@
     seasonData.flatMap((s) => s.episodes)
   );
 
+  const playLabel = $derived(item?.kind === "series" ? seriesPlayLabel(currentEpisode) : "Play");
+  // An empty series has nowhere for the hero button to lead.
+  const canPlay = $derived(item?.kind !== "series" || currentEpisode !== null);
+
   // Find the focused episode (check allEpisodes first, then fall back to directly fetched)
   const focusedEpisode = $derived(
     focusedEpisodeId
@@ -422,9 +456,11 @@
               {/if}
               {#if item.parentIndexNumber || item.indexNumber}
                 <p class="text-lg text-gray-400 mt-1">
-                  {#if item.seasonId && item.parentIndexNumber}
+                  <!-- Links to the season's place in the series list, not to a
+                       season page — seasons have none (DR-103). -->
+                  {#if item.seriesId && item.parentIndexNumber}
                     <a
-                      href={`/library/${item.seasonId}`}
+                      href={`/library/${item.seriesId}#${seasonAnchorId(item.parentIndexNumber)}`}
                       class="hover:underline hover:text-[var(--color-jellyfin)] transition-colors"
                     >Season {item.parentIndexNumber}</a>
                   {:else if item.parentIndexNumber}Season {item.parentIndexNumber}{/if}
@@ -466,15 +502,17 @@
 
           <!-- Actions -->
           <div class="flex gap-3 flex-wrap">
-            <button
-              onclick={handlePlayAll}
-              class="px-6 py-2 bg-[var(--color-jellyfin)] hover:bg-[var(--color-jellyfin-dark)] rounded-lg font-medium flex items-center gap-2 transition-colors"
-            >
-              <svg class="w-5 h-5" fill="currentColor" viewBox="0 0 24 24">
-                <path d="M8 5v14l11-7z"/>
-              </svg>
-              Play
-            </button>
+            {#if canPlay}
+              <button
+                onclick={handlePlayAll}
+                class="px-6 py-2 bg-[var(--color-jellyfin)] hover:bg-[var(--color-jellyfin-dark)] rounded-lg font-medium flex items-center gap-2 transition-colors"
+              >
+                <svg class="w-5 h-5" fill="currentColor" viewBox="0 0 24 24">
+                  <path d="M8 5v14l11-7z"/>
+                </svg>
+                {playLabel}
+              </button>
+            {/if}
             {#if item.kind !== "episode" && item.kind !== "movie"}
               <button
                 onclick={handleShufflePlay}
@@ -498,6 +536,12 @@
                 seriesName={item.name}
                 episodeCount={allEpisodes.length || undefined}
               />
+              <ClearHistoryButton
+                itemId={item.id}
+                itemName={item.name}
+                scope="series"
+                onCleared={loadItem}
+              />
             {:else if item.kind === "movie"}
               <VideoDownloadButton
                 itemId={item.id}
@@ -627,7 +671,11 @@
                   {season}
                   {episodes}
                   focusedEpisodeId={focusedEpisodeId ?? undefined}
+                  currentEpisodeId={currentEpisode?.id}
+                  expanded={expandedSeasons.has(season.id)}
+                  onToggle={() => toggleSeason(season.id)}
                   onEpisodeClick={handleEpisodeClick}
+                  onHistoryCleared={loadItem}
                 />
               {/each}
             {/if}