fix(player): stop AbortError storm from HLS stall recovery (DR-096)

Html5PlayerAdapter.play() reported every interrupted play attempt as a
player error. While an HLS stream stalls, hls.js' gap-controller nudges
the element to recover, which cancels the pending play() promise and
raises AbortError ("play() request was interrupted by a call to
pause()"). That is transient — the element is still trying to play — but
it hit host.onError roughly once a second for the whole stall, leaving
the UI stuck reporting paused.

Treat an interrupted play as a debug-level non-event, and memoise the
in-flight attempt so the UI and recovery paths share one element.play()
rather than stacking calls that abort each other.

This is the loop amplifier, complementing DR-095 which removed the
dead-segment stall that triggered it.

Note: webviewAudioAdapter.play() has the same raw shape but is not
implicated — audio playback does not go through hls.js — so it is left
unchanged rather than widening this fix.

docs/requirements.md

@@ -248,6 +248,7 @@ Internal architecture, components, and application logic.
 | DR-091 | Search result groups split TV into separate Shows and Episodes groups and add a People group (default order: Shows → Episodes → Movies → Songs → Albums → Artists → People); a stored `tvShows` order from before the split expands in place to shows+episodes so an upgrading user keeps their arrangement | UI | UR-060 | Done |
 | DR-092 | Video tap gestures resolve in `tapGestures.ts` (pure, unit-tested) rather than inline in `VideoPlayer.svelte`: `registerTap` returns `pending` for a first tap — the component defers `togglePlayPause` behind a `DOUBLE_TAP_WINDOW_MS` (300 ms) timer that a second tap cancels — or `seek` (+30 s right / −10 s left) for a second tap inside the window; a consumed second tap resets the state so a third tap starts fresh, and a swipe cancels the pending tap. The compatibility `click` the browser synthesizes after a touch tap is filtered in `handleVideoClick` so it cannot bypass the deferral. `resolveSeekTarget` converts the delta to the absolute position the facade requires, clamped per DR-095 and chained off a still-in-flight `pendingSeekTarget` so back-to-back skips accumulate instead of all resolving against a not-yet-updated position | UI | UR-061 | Done |
 | DR-094 | Frontend boundary tripwire (`scripts/check-frontend-boundary.sh`) detects Jellyfin item-type array literals **anywhere** in `src/` rather than only inline at an `includeItemTypes:` query site, so a category→type mapping cannot evade the check by being assigned to a named const (the evasion that let the `scoped-search` leak pass CI); requires two adjacent type literals so single-type presentation and `item.type ===` inspection stay legal, and caps the allowlist to force taxonomy into Rust instead of accumulating exceptions | Tooling | - | 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-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 |