Phase 2C WIP: PreviewOverlay modal + root integration (reel centering bug)

Working:
- PreviewOverlay.svelte mounted at app root; opens over a fixture manifest
  (window.__previewFixture(n) in dev), inert background, player bar hidden,
  focus trap, keyboard nav, F3 rail, T3 swaps, R1b capsule, accent extraction.
- previewSession.svelte.js: store + service wiring (production + fixture).
- Root integration in App.svelte; revision-gateway bumps + notePlaybackGeneration
  threaded through state.svelte.js player entry points; api.win guarded so plain
  vite browser mounts.
- Launcher on the artist page builds a real artist manifest and opens the modal
  with a play-full starter.
- 70 JS tests still green.

Two bugs found and fixed during bring-up:
- effect_update_depth_exceeded: bleed-crossfade and bump effects read AND wrote
  the same $state; wrapped writes in untrack(). This loop was breaking Svelte's
  scheduler globally (even ui.* stopped reacting).
- accentFromImage now sets crossOrigin for remote covers.

KNOWN BROKEN (handoff): reel vertical centering. The active card stays centred
at index 0 but drifts by one stride per step. Root cause isolated — see
TODO-Feature-Docs/scrollable-track-previews/HANDOFF-PHASE2C.md.

src/lib/state.svelte.js

@@ -1,6 +1,11 @@
 // Shared reactive app state (Svelte 5 runes module).
 import * as api from "./api.js";
 import { accentFromImage, hexToRgb, rgbToHex, lerpRgb } from "./color.js";
+import {
+    initPreviewBridge,
+    bumpMainRevision,
+    notePlaybackGeneration,
+} from "./preview/previewSession.svelte.js";
 
 export const app = $state({
     connection: "offline", // offline | connecting | online
@@ -3554,6 +3559,17 @@ export function initEvents() {
     if (started) return;
     started = true;
     initWindowActivity();
+    // Preview audio-focus bridge (scrollable-track-previews). Injected here
+    // rather than imported there: this module owns the player store, and the
+    // preview module must stay import-cycle-free. resumeMain goes straight to
+    // api — NOT through any wrapper that bumps the revision gateway, because
+    // a focus-internal resume must not invalidate its own token.
+    initPreviewBridge({
+        readPlayer: () => player,
+        resumeMain: () => {
+            api.playerControl("resume");
+        },
+    });
 
     // The `connected` event fires once, at login. A WebView reload (dev
     // iteration, crash recovery) lands AFTER it, so the fresh frontend
@@ -3620,6 +3636,19 @@ export function initEvents() {
     });
 
     api.onEvent("soulseek:player", (ev) => {
+        // Revision-gateway bumps at the ONE choke point every native source
+        // change flows through. Each new decode ("buffering") is a new
+        // playback generation for the focus bridge; track-ended is the
+        // auto-advance revision. A pause caused by the focus coordinator
+        // emits "paused", which deliberately bumps nothing.
+        if (ev.kind === "buffering") {
+            notePlaybackGeneration();
+            bumpMainRevision("nativeSourceChange");
+        } else if (ev.kind === "track-ended") {
+            bumpMainRevision("autoAdvance");
+        } else if (ev.kind === "stopped") {
+            bumpMainRevision("userStop");
+        }
         switch (ev.kind) {
             case "buffering":
                 player.status = "buffering";
@@ -3835,6 +3864,7 @@ export async function streamFile(username, file, subLabel) {
 
 /** Play a finished download from disk (single track). */
 export async function playLocalFile(path, title, subLabel, artPath = null) {
+    bumpMainRevision("userPlay");
     autoAlbum = null;
     player.queue = [{ path, title, sub: subLabel ?? "", duration: null, art: artPath, quality: localQuality({ path }) }];
     player.queueIndex = 0;
@@ -3867,6 +3897,10 @@ export function playAlbum(tracks, subLabel, start = 0, artPath = null) {
 function playQueueIndex(i) {
     const item = player.queue[i];
     if (!item) return;
+    // Every queue start is a user-command + queue + playback revision for the
+    // preview focus gateway (auto-advance re-enters here too — that bump is
+    // correct: a restore must never resurrect a track the queue moved past).
+    bumpMainRevision("queueJumpOrNextPrev");
     player.queueIndex = i;
     player.track = {
         title: item.title,