fix(player): re-entering a video no longer opens the audio player (DR-100)

Leaving a video and returning to it rendered the movie/episode in
AudioPlayer. Closing a webview-rendered video deliberately emits no
"stopped" state (that would break the autoplay handoff), and the
direct-play path does not stop the backend on unmount, so the Rust
controller still reported that item as its loaded media. Re-entering the
route therefore took the "already playing, just show the UI" shortcut,
which returns before a stream URL is fetched, and the render fell
through to the audio surface. Mostly visible on Android, where video
direct-plays; Linux transcodes and stops the backend on unmount.

Both decisions move into playerSurface.ts as pure functions:
shouldReuseActivePlayback excludes video, so video always takes the full
load path and gets its stream URL and resume position;
resolvePlayerSurface maps video-without-a-stream-URL to "pending"
(spinner) rather than falling through to audio.

docs/requirements.md

@@ -253,6 +253,7 @@ Internal architecture, components, and application logic.
 | DR-097 | Transport authority (play/pause/toggle) lives in Rust for **webview-rendered** media, not just native. The controller tracks the state the HTML5 element reports (`html5_playing`, fed by `report_html5_state`, which now *stores* rather than only re-emitting); `play`/`pause`/`toggle_playback` consult it and drive the element by emitting a `ControlCommand` that `playerEvents.handleControlCommand` executes against the active adapter. A `stopped`/`idle` report clears it so the native backend (MPV/ExoPlayer) regains authority for music. The frontend facade no longer short-circuits transport into the adapter: `adapter.toggle()` previously decided play-vs-pause by reading `el.paused` off the DOM, a value that flips transiently while an element buffers or settles a seek — so two intents ~150 ms apart read *different* values, performed *opposing* actions, and self-sustained a play/pause loop needing no further input (observed on Android with a fully-buffered `readyState=4 networkState=1` element). Same "backend decides, adapter executes the primitive" split as `player_seek_video` | Player | UR-005 | Done |
 | DR-096 | `Html5PlayerAdapter.play()` is resilient to stall recovery: an in-flight attempt is memoised so concurrent callers (UI plus hls.js gap-controller recovery) share one `element.play()` instead of stacking calls, and an `AbortError` ("play() request was interrupted by a call to pause()") is logged at debug rather than pushed to `host.onError`. The browser raises it whenever a pending play promise is superseded by a pause/seek/source change, which hls.js does routinely while nudging past a stall — reporting it surfaced a player error roughly once per second for the whole stall and left the UI stuck showing paused | Player | UR-005 | Done |
 | DR-095 | Seek targets clamp strictly *inside* the media (`clampSeekTarget`, `END_SEEK_MARGIN_SECONDS` = 6 s ≈ one HLS segment) instead of to the exact `duration`. Landing on the duration makes hls.js request the segment whose start time lies past the end of the media (e.g. a 6330.324 s item → segment 1055 starting at 6336.33 s), which Jellyfin never produces; the fetch times out and hls.js' gap-controller stalls at the last buffered position, presenting as "unpausing or skipping bounces straight back to paused". Applied on both seek paths — the relative-skip `resolveSeekTarget` and the seek-bar drag, whose range input `max` is the duration itself — and floored at 0 so media shorter than the margin still seeks to the start | UI | UR-061 | Done |
+| DR-100 | Leaving a video and re-entering it renders the **video** player, never the audio one. Both halves of the `/player/[id]` decision are pure and unit-tested in `playerSurface.ts`. (a) `shouldReuseActivePlayback` excludes video: the "already playing, just show the UI" shortcut (added for expanding the audio mini player) returns *before* a stream URL is fetched, which is fine for audio — the backend owns the stream and the route only mirrors it — but leaves `<VideoPlayer>` with nothing to render. Closing a webview-rendered video deliberately emits no `stopped` state (that would break the autoplay handoff, see DR-047), so the Rust controller still reports that movie/episode as its loaded media and re-entering the same item hit the shortcut. (b) `resolvePlayerSurface` maps video-without-a-stream-URL to `pending` (spinner) instead of falling through to `<AudioPlayer>`, so no future path can put video content in the audio surface. Video now always takes the full load path, which fetches the stream URL and applies the stored resume position | UI | UR-005 | Done |
 | DR-093 | Traceability coverage gate derives its requirement denominators from `requirements.md` at run time rather than hardcoded literals: `countDefinedRequirements` counts an ID only where it leads a markdown table row (ignoring the "Traces To" column and prose) and deduplicates IDs listed both in the definition tables and in the §3 traceability matrix; `computeCoverage` reports the *intersection* of traced and defined IDs so an ID traced in code but absent from `requirements.md` is surfaced as `orphaned` instead of inflating the ratio past 100%. UT/IT test identifiers are excluded as a separate taxonomy. CI and `bun run traces:coverage` share this computation and fail on both a sub-threshold and an impossible >100% result | Tooling | - | Done |
 
 ---
@@ -420,6 +421,8 @@ Internal architecture, components, and application logic.
 | UT-089 | A touch drag on the video seek bar seeks to the dragged position, never toggles play/pause, and never alters brightness — the container gesture layer stays out of a control drag entirely | DR-098, DR-099 | Done |
 | UT-090 | The seek bar commits its seek on `touchend` even when the engine never fires `change`, and commits exactly once when both signals arrive | DR-099 | Done |
 | UT-091 | Transport intents (play/pause/toggle) reach the backend even while a video adapter is registered, and never call the adapter's own `play`/`pause`/`toggle` — the webview must not decide play-vs-pause from the DOM | DR-097 | Done |
+| UT-092 | `shouldReuseActivePlayback` reuses backend playback for an already-loaded audio track but never for video, and never when an explicit start position or a next-episode restart was requested | DR-100 | Done |
+| UT-093 | `resolvePlayerSurface` returns `video` only with a stream URL, `pending` for video whose stream URL is still missing (never `audio`), and `audio` for audio content | DR-100 | Done |
 
 ### Integration Tests