fix: prevent notification close on skip and background audio stall

- playCurrent: set _trackChanging flag and update media session metadata
  before changing src, so the pause event fired by src-swap does not
  set playbackState='paused' and dismiss the Samsung cover screen notification
- Remove stalled->load() handler that silently paused audio with no recovery
- Error handler now retries regardless of paused state (load() causes paused)
- Add .catch() to audio.play() in playCurrent

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/gen-icons.mjs

@@ -0,0 +1,19 @@
+// Run: node scripts/gen-icons.mjs
+// Generates public/icon-192.png and public/icon-512.png from public/icon.svg
+// Requires: npm install --save-dev sharp
+
+import sharp from 'sharp';
+import { readFileSync } from 'fs';
+import { fileURLToPath } from 'url';
+import { dirname, join } from 'path';
+
+const root = join(dirname(fileURLToPath(import.meta.url)), '..');
+const svg = readFileSync(join(root, 'public/icon.svg'));
+
+for (const size of [192, 512]) {
+  await sharp(svg)
+    .resize(size, size)
+    .png()
+    .toFile(join(root, `public/icon-${size}.png`));
+  console.log(`icon-${size}.png created`);
+}