feat(now-playing): OpenSubsonic playbackReport for live now-playing (#1080)

* feat(now-playing): adopt OpenSubsonic playbackReport for live now-playing

Drive a small playback state machine (starting → playing ↔ paused → stopped)
on the Subsonic-server channel when the server advertises the OpenSubsonic
`playbackReport` extension (Navidrome ≥ 0.62), giving `getNowPlaying` a real
transport state and an extrapolated position. Reports send `ignoreScrobble=true`
so play counts stay on the existing `scrobble.view` 50% path (no double count),
and the effective playback speed is included so the server extrapolates position
correctly with the speed feature on.

- New `playbackReportSession` FSM mirrors the existing `playListenSession`
  lifecycle hooks and is wired at the same player call sites (start / gapless
  switch / queue restore / resume / 15s heartbeat / pause / seek / stop / ended /
  error / app quit). Servers without the extension degrade to the unchanged
  legacy `scrobble.view?submission=false` presence call.
- Gated through the existing serverCapabilities framework: a new
  `FEATURE_PLAYBACK_REPORT` (auto, extension-detected). The OpenSubsonic
  extensions probe now stores the full advertised list once and serves both
  AudioMuse `sonicSimilarity` and `playbackReport` from it, without disturbing
  the legacy Instant Mix opt-in on pre-0.62 servers.
- Now Playing dropdown shows a live position bar and a paused indicator.
- reportPlayback uses the real request params (mediaId / mediaType / positionMs).

Tests: FSM transitions + gating + legacy fallback, capability resolution,
extension-list probe storage/decoupling. Full suite green; no Tauri-boundary
changes.

* feat(now-playing): glide the Live position bar between polls

Extrapolate the position of `playing` entries locally (elapsed × reported
playbackRate from the last 10 s poll) and re-render once a second, so the Live
progress bar advances smoothly instead of jumping on each refresh. Paused and
position-less entries stay frozen. A linear width transition matched to the tick
keeps the fill gliding. Only applies to clients that report a position via the
playbackReport extension.

* fix(now-playing): tighten Live timer layout and report resume immediately

Keep the progress-bar width stable without a wide empty gap before the
timer: reserve ~2ch inside the current-time span only (right-aligned), not
on the whole clock block. Report `playing` to the server as soon as
resume() runs, matching the immediate `paused` report on pause instead of
waiting for the Rust `audio:playing` event.

* docs: CHANGELOG and credits for playbackReport live now-playing (PR #1080)

src/serverCapabilities/catalog.ts

@@ -13,14 +13,17 @@ import type { CapabilityDefinition } from './types';
  */
 
 export const SONIC_SIMILARITY_EXTENSION = 'sonicSimilarity';
+export const PLAYBACK_REPORT_EXTENSION = 'playbackReport';
 
 export const FEATURE_AUDIOMUSE_SIMILAR_TRACKS = 'audiomuse.similarTracks';
+export const FEATURE_PLAYBACK_REPORT = 'opensubsonic.playbackReport';
 
 export const PROBE_OPENSUBSONIC_EXTENSIONS = 'opensubsonic.extensions';
 export const PROBE_LEGACY_INSTANT_MIX = 'navidrome.instantMix.legacy';
 
 /** Operation names used by the call router. */
 export const OP_SIMILAR_TRACKS = 'similarTracks';
+export const OP_REPORT_PLAYBACK = 'reportPlayback';
 
 export const SERVER_CAPABILITY_CATALOG: CapabilityDefinition[] = [
   {
@@ -65,6 +68,32 @@ export const SERVER_CAPABILITY_CATALOG: CapabilityDefinition[] = [
       },
     ],
   },
+  {
+    // OpenSubsonic `playbackReport` (Navidrome ≥ 0.62): rich live now-playing via
+    // a small playback FSM. Auto-on wherever the server advertises the extension;
+    // call sites fall back to legacy `scrobble.view?submission=false` presence when
+    // it is absent. Detection is server-agnostic (any OpenSubsonic server may add it).
+    feature: FEATURE_PLAYBACK_REPORT,
+    labelKey: 'nowPlaying.title',
+    strategies: [
+      {
+        id: 'opensubsonic.playbackReport',
+        priority: 100,
+        when: (ctx) => ctx.openSubsonic,
+        detection: {
+          kind: 'extension',
+          probeId: PROBE_OPENSUBSONIC_EXTENSIONS,
+          extension: PLAYBACK_REPORT_EXTENSION,
+        },
+        trust: 'high',
+        activation: 'auto',
+        calls: {
+          [OP_REPORT_PLAYBACK]: { endpoint: 'reportPlayback.view', transport: 'opensubsonic' },
+        },
+        labelKey: 'nowPlaying.title',
+      },
+    ],
+  },
 ];
 
 export function getCapabilityDefinition(feature: string): CapabilityDefinition | undefined {