feat(home): tap opens detail, long-press plays from home cards

Home carousel cards route a tap to the item's detail / Episode Focus
View and a ~500ms long-press to a confirm-then-play flow. MediaCard gains
an onLongPress prop with pointer-based detection (cancelled on >10px move
so carousel scroll is unaffected, trailing click suppressed). Episode
taps route to /library/<seriesId>?episode=<id>; the bare-episode detail
page links back to its parent series/season.

TRACES: UR-058 | DR-087

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

@@ -381,12 +381,29 @@
         <div class="flex-1 space-y-4">
           <div>
             <h1 class="text-3xl font-bold text-white">{item.name}</h1>
-            {#if item.kind === "episode" && (item.parentIndexNumber || item.indexNumber)}
-              <p class="text-lg text-gray-400 mt-1">
-                {#if item.parentIndexNumber}Season {item.parentIndexNumber}{/if}
-                {#if item.parentIndexNumber && item.indexNumber}, {/if}
-                {#if item.indexNumber}Episode {item.indexNumber}{/if}
-              </p>
+            {#if item.kind === "episode"}
+              <!-- Links back to the parent series/season so the episode detail
+                   page is a navigable hub, not a dead end. TRACES: UR-058 | DR-087 -->
+              {#if item.seriesId && item.seriesName}
+                <p class="text-lg mt-1">
+                  <a
+                    href={`/library/${item.seriesId}`}
+                    class="text-[var(--color-jellyfin)] hover:underline"
+                  >{item.seriesName}</a>
+                </p>
+              {/if}
+              {#if item.parentIndexNumber || item.indexNumber}
+                <p class="text-lg text-gray-400 mt-1">
+                  {#if item.seasonId && item.parentIndexNumber}
+                    <a
+                      href={`/library/${item.seasonId}`}
+                      class="hover:underline hover:text-[var(--color-jellyfin)] transition-colors"
+                    >Season {item.parentIndexNumber}</a>
+                  {:else if item.parentIndexNumber}Season {item.parentIndexNumber}{/if}
+                  {#if item.parentIndexNumber && item.indexNumber}, {/if}
+                  {#if item.indexNumber}Episode {item.indexNumber}{/if}
+                </p>
+              {/if}
             {:else if item.artistItems?.length || item.artists?.length}
               <p class="text-lg text-gray-400 mt-1">
                 <ArtistLinks