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-tauri/src/commands/player/mod.rs

@@ -347,7 +347,7 @@ pub enum AudioTrackSwitchResponse {
 /// 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
 #[derive(specta::Type, Debug, Serialize)]
 #[serde(tag = "strategy", rename_all = "camelCase")]
 pub enum StreamQualityResponse {
@@ -1485,7 +1485,7 @@ pub async fn player_switch_audio_track(
 /// 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
 #[tauri::command]
 #[specta::specta]
 pub async fn player_set_stream_quality(