feat(playback): shared player store to sync transcript<->audio (FR-REC-5)

src/lib/stores/player.svelte.ts

@@ -0,0 +1,29 @@
+// Shared recording-playback state so the transcript (center pane,
+// TranscriptNotes) and the <audio> element (side pane, SummaryPanel) can talk
+// to each other across the App layout: click a transcript segment to seek the
+// player, and highlight/auto-scroll the segment that's currently playing.
+// Pure UI ephemera — no persistence, reset per meeting.
+
+class PlayerStore {
+  /** Playback position in ms, pushed from the <audio> element's timeupdate. */
+  currentMs = $state(0);
+  /** Target of the latest seek request, in ms. */
+  seekMs = $state<number | null>(null);
+  /** Bumped on every seek() so clicking the *same* segment twice re-seeks
+   * (a plain seekMs assignment wouldn't fire when the value is unchanged). */
+  seekNonce = $state(0);
+
+  /** Ask the player to jump to `ms` and play (SummaryPanel watches seekNonce). */
+  seek(ms: number) {
+    this.seekMs = ms;
+    this.seekNonce++;
+  }
+
+  /** Clear when the selected meeting changes so a new recording starts at 0. */
+  reset() {
+    this.currentMs = 0;
+    this.seekMs = null;
+  }
+}
+
+export const player = new PlayerStore();