fix(player): restore the subtitle sidecar work dropped by the previous commit

The previous commit was assembled from a tree read before 13264e22 landed,
so committing it reverted that commit's changes: the image-based subtitle
filtering in device_profile/types, subtitleTracks and its tests, the
regenerated bindings, and the VideoPlayer menu wiring.

Nothing was lost — the working tree held both changes throughout. This
restores those files to the merged state, leaving both the subtitle fix and
the play-session fix in place.

TRACES: UR-020, UR-004 | DR-176 | UT-168

src/lib/components/player/VideoPlayer.svelte

@@ -16,6 +16,7 @@
   import { videoFitClass } from "./videoFit";
   import { fatalNetworkErrorAction } from "./hlsRecovery";
   import {
+    subtitleStreamsOf,
     resolveSubtitleTracks,
     reconcileSelectedSubtitle,
     videoCrossOriginMode,
@@ -333,13 +334,18 @@
     }
   }
 
-  // Get available subtitle tracks from media streams
+  // The subtitle streams the menu offers — the same list the <track> children
+  // and the native play request are built from, so the menu can never name a
+  // track the player was never given. subtitleStreamsOf() also drops the ones
+  // the backend says it cannot deliver as a sidecar (image-based PGS/DVD/DVB,
+  // which only server burn-in could show and we never ask for — DR-176).
+  // TRACES: UR-020 | DR-176 | UT-168
   const subtitleTracks = $derived(() => {
     if (!media || !media.mediaStreams) {
       console.log("[VideoPlayer] No media or mediaStreams available for subtitles");
       return [];
     }
-    const tracks = media.mediaStreams.filter(stream => stream.kind === "subtitle");
+    const tracks = subtitleStreamsOf(media.mediaStreams);
     console.log("[VideoPlayer] Found subtitle tracks:", tracks.length, tracks);
     return tracks;
   });

src/lib/components/player/subtitleTracks.test.ts

@@ -53,6 +53,68 @@ describe("subtitleStreamsOf", () => {
     expect(subtitleStreamsOf(null)).toEqual([]);
     expect(subtitleStreamsOf(undefined)).toEqual([]);
   });
+
+  /**
+   * A subtitle the app cannot draw must not reach the picker. Image-based
+   * tracks (PGS/DVD/DVB) are bitmaps: the only way to show one is for the server
+   * to composite it into the video, which this app deliberately never asks for
+   * (DR-176). Offering it anyway produced the reported symptom's twin — a menu
+   * entry that selects, ticks, and shows nothing.
+   *
+   * The verdict is the backend's (`supportsExternalDelivery`); the codec
+   * vocabulary behind it stays in Rust.
+   *
+   * TRACES: UR-020 | DR-176 | UT-168
+   */
+  it("drops subtitles the backend says it cannot deliver as a sidecar", () => {
+    const streams: SubtitleStreamLike[] = [
+      { index: 2, kind: "subtitle", displayTitle: "English PGS SDH", supportsExternalDelivery: false },
+      { index: 3, kind: "subtitle", displayTitle: "English Text SDH", supportsExternalDelivery: true },
+    ];
+
+    expect(subtitleStreamsOf(streams).map((s) => s.index)).toEqual([3]);
+  });
+
+  /**
+   * Only an explicit "no" hides a track. A stream that carries no verdict at all
+   * predates the field (or came from somewhere that does not set it), and
+   * hiding those would silently empty the menu for sources that work today.
+   *
+   * TRACES: UR-020 | DR-176 | UT-168
+   */
+  it("keeps subtitles that carry no verdict", () => {
+    const streams: SubtitleStreamLike[] = [
+      { index: 2, kind: "subtitle", displayTitle: "English" },
+      { index: 3, kind: "subtitle", displayTitle: "French", supportsExternalDelivery: null },
+    ];
+
+    expect(subtitleStreamsOf(streams).map((s) => s.index)).toEqual([2, 3]);
+  });
+
+  /**
+   * The same list feeds the `<track>` children and the native play request, so
+   * an undeliverable track must not even have its URL fetched — that request is
+   * the one that 404s, and the sideloaded track it would produce is the dead
+   * entry all over again.
+   *
+   * TRACES: UR-020 | DR-176 | UT-168
+   */
+  it("never resolves a URL for a subtitle it dropped", async () => {
+    const asked: number[] = [];
+    const tracks = await resolveSubtitleTracks(
+      [
+        { index: 2, kind: "subtitle", displayTitle: "PGS", supportsExternalDelivery: false },
+        { index: 3, kind: "subtitle", displayTitle: "SRT", supportsExternalDelivery: true },
+      ],
+      async (index) => {
+        asked.push(index);
+        return url(index);
+      },
+    );
+
+    expect(asked).toEqual([3]);
+    expect(tracks.map((t) => t.streamIndex)).toEqual([3]);
+  });
 });
 
 describe("subtitleTrackLabel", () => {

src/lib/components/player/subtitleTracks.ts

@@ -32,6 +32,13 @@ export interface SubtitleStreamLike {
   displayTitle?: string | null;
   isDefault?: boolean;
   isForced?: boolean;
+  /**
+   * The backend's verdict on whether this track can arrive as a sidecar the app
+   * renders itself. `false` means only the server could have shown it, by
+   * burning it into the picture — which the app never asks for. Absent means no
+   * verdict was given, which is not the same as "no".
+   */
+  supportsExternalDelivery?: boolean | null;
 }
 
 /** A subtitle stream whose URL resolved — i.e. one we can actually render. */
@@ -46,12 +53,32 @@ export interface RenderableSubtitleTrack {
   isDefault: boolean;
 }
 
-/** Subtitle streams of a media item, in stream order. */
-export function subtitleStreamsOf(
-  streams: readonly SubtitleStreamLike[] | null | undefined,
-): SubtitleStreamLike[] {
+/**
+ * Subtitle streams of a media item that the app can actually show, in stream
+ * order. This is the one list behind everything: the picker, the `<track>`
+ * children, and the array sent to the native backend.
+ *
+ * Image-based subtitles (PGS/DVD/DVB) are filtered out here rather than at each
+ * consumer. They are bitmaps — a client can only display one if the server
+ * composites it into the video, and the app deliberately asks for no burn-in at
+ * all (DR-176), so such a track is one it can never draw. Leaving it in the
+ * picker produced a control that ticked and showed nothing.
+ *
+ * The judgement is the backend's: `supportsExternalDelivery` arrives already
+ * decided, because *which formats are bitmaps* is domain vocabulary and belongs
+ * in Rust. Only an explicit `false` drops a stream; a stream carrying no verdict
+ * is kept, so a source that never sets the field behaves exactly as before.
+ *
+ * Generic in the stream type so callers keep their own richer fields (the menu
+ * reads `codec` off the result).
+ *
+ * TRACES: UR-020 | DR-176 | UT-168
+ */
+export function subtitleStreamsOf<T extends SubtitleStreamLike>(
+  streams: readonly T[] | null | undefined,
+): T[] {
   if (!streams) return [];
-  return streams.filter((s) => s.kind === "subtitle");
+  return streams.filter((s) => s.kind === "subtitle" && s.supportsExternalDelivery !== false);
 }
 
 /** Human label for a subtitle stream, matching the menu's own fallback chain. */