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.

tests/contrast.mjs

@@ -43,6 +43,7 @@ const screens = [
   ["chat", "/chat", null],
   ["stats", "/stats", null],
   ["exam", "/exam", null],
+  ["podcast", "/podcast/pod_contrast", null],
   ["settings", "/", "settings"],
   ["notfound", "/no-such-page", null],
 ];
@@ -51,7 +52,27 @@ for (const [label, path, mode] of screens) {
   if (filter && !label.includes(filter)) continue;
   for (const theme of ["dark", "light", "aero"]) {
     const { context, page } = await makePage(browser, { width: 390, height: 844, deviceScaleFactor: 1 });
-    await seed(page, { decks: [DECK], theme });
+    await seed(page, {
+      decks: [DECK],
+      theme,
+      extra: {
+        "freezmo.podcasts.v1": JSON.stringify([
+          {
+            id: "pod_contrast",
+            title: "Why the sky is blue",
+            summary: "Rayleigh scattering, explained out loud.",
+            language: "English",
+            sourceText: "Rayleigh scattering makes the sky blue.",
+            createdAt: 1,
+            updatedAt: 1,
+            sections: [
+              { heading: "Daylight", text: "Look up on a clear day. The sky is blue — a blue so obvious that it is easy to stop asking why." },
+              { heading: "Why", text: "Tiny molecules scatter short wavelengths far more than long ones." },
+            ],
+          },
+        ]),
+      },
+    });
     await page.goto(`${BASE}${path}`, { waitUntil: "networkidle" });
     await page.waitForTimeout(1000);
     if (mode === "settings") {