docs(player): allocate UR-074/DR-162 for the streaming bitrate cap

The feature shipped tagged against DR-160, which a parallel session had
claimed for picture-in-picture in the meantime. Renumbered to DR-162
across the Rust and frontend TRACES comments (the PiP tags in
VideoPlayer.svelte, pictureInPicture.ts and nativeVideo.ts keep DR-160)
and regenerated bindings.ts.

Adds the requirement rows the tags point at: UR-074 for the user need, and
DR-162 covering why the cap has to reach the PlaybackInfo negotiation and
not only the transcode URL, why the ceiling is process-wide, and why the
Settings default persists while the in-player override does not. Notes
that this gives UR-070 its resume-at-the-same-point mechanism while the
server-offered rendition list that requirement also asks for stays
proposed. UT-156/157 record what the tests pin.

docs/specs/streaming-bitrate-cap.md carries the layer assignment — the
step definitions, the video/audio split, the resolution pairing and the
reload decision are all Rust; the frontend holds a serde token and the
labels it was handed.

TRACES: UR-074 | DR-162 | UT-156, UT-157

src/lib/api/bindings.ts

@@ -205,7 +205,7 @@ async playerGetVideoSettings() : Promise<VideoSettings> {
  * frontend reads them here rather than encoding them — the same arrangement as
  * [`player_get_eq_presets`].
  * 
- * TRACES: UR-074 | DR-160
+ * TRACES: UR-074 | DR-162
  */
 async playerGetStreamingQualities() : Promise<([StreamingQuality, string, string])[]> {
     return await TAURI_INVOKE("player_get_streaming_qualities");
@@ -226,7 +226,7 @@ async playerGetStreamingQualities() : Promise<([StreamingQuality, string, string
  * durable default belongs to Settings. `player_set_video_settings` is the one
  * that writes to the database.
  * 
- * TRACES: UR-074 | DR-160
+ * TRACES: UR-074 | DR-162
  */
 async playerSetStreamQuality(repositoryHandle: string, quality: StreamingQuality, useHtml5: boolean, currentPosition: number | null, mediaSourceId: string | null, audioStreamIndex: number | null) : Promise<StreamQualityResponse> {
     return await TAURI_INVOKE("player_set_stream_quality", { repositoryHandle, quality, useHtml5, currentPosition, mediaSourceId, audioStreamIndex });
@@ -2897,7 +2897,7 @@ export type StreamKind = "audio" | "video" | "subtitle" |
  * Mirrors [`AudioTrackSwitchResponse`]: the backend decides whether the caller
  * has to reload anything, so no strategy branch lives in the UI.
  * 
- * TRACES: UR-074 | DR-160
+ * TRACES: UR-074 | DR-162
  */
 export type StreamQualityResponse = 
 /**
@@ -2922,7 +2922,7 @@ export type StreamQualityResponse =
  * bitrate so the encoder does not spend a small budget on pixels it cannot
  * afford. See docs/specs/streaming-bitrate-cap.md.
  * 
- * TRACES: UR-074 | DR-160
+ * TRACES: UR-074 | DR-162
  */
 export type StreamingQuality = 
 /**
@@ -3057,7 +3057,7 @@ autoPlayMaxEpisodes?: number;
  * `#[serde(default)]` so settings JSON persisted before this field existed
  * loads as the previous behaviour (uncapped).
  * 
- * TRACES: UR-074 | DR-160
+ * TRACES: UR-074 | DR-162
  */
 streamingQuality?: StreamingQuality }
 /**

src/lib/components/player/VideoPlayer.scrubRegression.test.ts

@@ -82,6 +82,10 @@ vi.mock("$lib/api/bindings", () => ({
     playerCancelSleepTimer: (...a: any[]) => playerCancelSleepTimer(...(a as [])),
     playerSetSubtitleTrack: vi.fn(async () => ({})),
     playerSwitchAudioTrack: vi.fn(async () => ({})),
+    // The player loads the streaming-quality picker on mount; without these the
+    // mock throws and every test in the file fails before it starts.
+    playerGetStreamingQualities: vi.fn(async () => []),
+    playerGetVideoSettings: vi.fn(async () => ({ streamingQuality: "original" })),
     storageGetSeriesAudioPreference: vi.fn(async () => null),
     storageSaveSeriesAudioPreference: vi.fn(async () => ({})),
   },

src/lib/components/player/VideoPlayer.svelte

@@ -246,7 +246,7 @@
 
   // Streaming bandwidth ceiling. The ladder and the current value both come from
   // Rust — the frontend never encodes what a step means.
-  // TRACES: UR-074 | DR-160
+  // TRACES: UR-074 | DR-162
   let showQualityMenu = $state(false);
   let streamingQualities = $state<[StreamingQuality, string, string][]>([]);
   let selectedQuality = $state<StreamingQuality>("original");
@@ -653,7 +653,7 @@
   // flips the component into HTML5 mode and breaks native seeking, and nothing
   // about playback waits on this list.
   //
-  // TRACES: UR-074 | DR-160
+  // TRACES: UR-074 | DR-162
   onMount(() => {
     Promise.all([
       commands.playerGetStreamingQualities(),
@@ -1929,7 +1929,7 @@
    * only supplies the position to resume at and reverts the selection if the
    * switch fails.
    *
-   * TRACES: UR-074 | DR-160
+   * TRACES: UR-074 | DR-162
    */
   async function selectQuality(quality: StreamingQuality) {
     showQualityMenu = false;
@@ -2354,7 +2354,7 @@
           </div>
         {/if}
 
-        <!-- Streaming quality (bandwidth ceiling). TRACES: UR-074 | DR-160 -->
+        <!-- Streaming quality (bandwidth ceiling). TRACES: UR-074 | DR-162 -->
         {#if streamingQualities.length > 0}
           <div class="relative">
             <button

src/lib/components/player/VideoPlayer.touchScrub.test.ts

@@ -84,6 +84,10 @@ vi.mock("$lib/api/bindings", () => ({
     playerCancelSleepTimer: vi.fn(async () => ({})),
     playerSetSubtitleTrack: vi.fn(async () => ({})),
     playerSwitchAudioTrack: vi.fn(async () => ({})),
+    // The player loads the streaming-quality picker on mount; without these the
+    // mock throws and every test in the file fails before it starts.
+    playerGetStreamingQualities: vi.fn(async () => []),
+    playerGetVideoSettings: vi.fn(async () => ({ streamingQuality: "original" })),
     storageGetSeriesAudioPreference: vi.fn(async () => null),
     storageSaveSeriesAudioPreference: vi.fn(async () => ({})),
   },

src/lib/player/index.ts

@@ -189,7 +189,7 @@ async function switchAudioTrack(
  * backend itself, and hands HTML5 a URL for the same `reloadSource` primitive
  * the audio-track switch uses. Requires an active video adapter.
  *
- * TRACES: UR-074 | DR-160
+ * TRACES: UR-074 | DR-162
  */
 async function setStreamQuality(
   quality: StreamingQuality,

src/routes/settings/+page.svelte

@@ -68,7 +68,7 @@
 
   // Bandwidth ceilings offered by the streaming-quality picker, as
   // [variant, label, detail] — the numbers behind each step are Jellyfin
-  // encoding vocabulary, so Rust serves the list. TRACES: UR-074 | DR-160
+  // encoding vocabulary, so Rust serves the list. TRACES: UR-074 | DR-162
   let streamingQualities = $state<[StreamingQuality, string, string][]>([]);
 
   // Download/caching behaviour, incl. the WiFi-only gate (UR-053).
@@ -340,7 +340,7 @@
     persistVideo();
   }
 
-  /** TRACES: UR-074 | DR-160 */
+  /** TRACES: UR-074 | DR-162 */
   function handleStreamingQualityChange(quality: StreamingQuality) {
     videoSettings.streamingQuality = quality;
     persistVideo();
@@ -698,7 +698,7 @@
 
         <!-- Streaming quality: the bandwidth ceiling every video stream is
              opened against. The steps and their labels come from Rust.
-             TRACES: UR-074 | DR-160 -->
+             TRACES: UR-074 | DR-162 -->
         <div class="bg-[var(--color-surface)] rounded-lg p-6 mt-4">
           <h3 class="text-xl font-semibold text-white">Streaming Quality</h3>
           <p class="text-sm text-gray-400 mt-1 mb-4">