Podcast mode: notes read aloud with a lyric-style word highlight

The third segment of the note-powered wizards (Study deck / Homework /
Podcast) takes the same intake - photos, documents, pasted text, the share
target - and turns it into a spoken episode.

- prompts: PODCAST_SYSTEM_PROMPT writes for the ear (plain prose, no markdown,
  no visual references), chaptered into 3-8 sections around a length target.
- /api/podcast mirrors /api/generate's plumbing (rate limit, model gate,
  provider keys, heartbeats, the 2x deadline, the optional vision pass).
- storage: frezmo.podcasts.v1, zod-validated, included in the backup and the
  encrypted sync payload; a new library tab lists episodes with listen /
  rename / delete-with-undo, and the wizard switch deep-links in.
- player: the transcript is word-wrapped spans and the word under the voice
  rides a lyric-style highlight that keeps itself centred. Two clocks: exact
  onboundary events where the browser reports them, a per-word length timer
  where it does not (iOS Safari); the first boundary retires the timer.
  Pause = cancel + re-speak from the word, which makes resume, chapter jumps
  and tap-any-word-to-seek the same operation; the position saves on pause,
  page-hide and unmount, so reopening resumes. Speed rebuilds the engine and
  keeps playing; the Aero soundtrack pauses itself when the voice starts; a
  browser with no voice gets an honest note and a readable transcript.
- the script sits on a glass pane (plain paragraphs over Aero's grass failed
  contrast; the scan now covers the player too).

tests/podcast-test.mjs (17th suite) stubs the model and the speech engine and
drives the highlight by hand: 26 checks. All suites green, contrast clean.
Version 0.7.3, SW v95.

app/globals.css

@@ -1306,6 +1306,23 @@ body:has(.scene-pause) .ice-scene :is(.ice-orb, .ice-bubble) {
   .chip { min-height: 44px; }
 }
 
+/* Podcast transcript: the word under the voice rides a highlight, the way
+   lyrics do in Spotify. Words are plain spans; the player flips one class. */
+.podcast-word {
+  border-radius: 0.4rem;
+  transition: background-color 140ms ease, color 140ms ease;
+  cursor: pointer;
+}
+.podcast-word-active,
+.podcast-word:hover {
+  background: var(--nav-active-bg);
+  color: var(--text);
+  box-shadow: 0 0 0 2px var(--nav-active-bg);
+}
+.podcast-word-active {
+  font-weight: 600;
+}
+
 /* The AI note under a surface that shows model output -------------------- */
 .ai-disclaimer {
   font-size: 12px;