feat(shorts): cinematic v2 visual design + synced karaoke captions

- Fix critical bug: scenes were stacked without <Sequence> — every segment
  rendered simultaneously, last scene covering the whole video (root cause
  of 'too simple/ugly' visual)
- Scene variety: kinetic word-by-word title (hook), karaoke caption card,
  big-number stat scene (auto-detected: $12B, 65%, 3.2M), CTA center
- Karaoke captions synced to TTS: edge-tts SentenceBoundary timing via new
  scripts/tts-words.py (mp3 + sentences.json per segment); active sentence
  bright, others dimmed
- Rich background per scene: 4 color palettes (indigo/pink, cyan/teal,
  purple/pink, orange/red), drifting orbs, dot grid, ken-burns motion
- Real fonts: @fontsource Inter 700 + Montserrat 800 (display/captions)
- Glass card captions, progress bar per-scene, safe zone 900x1400
- Word-boundary truncation for stat labels (no mid-word cuts)
- Perf kept: no blur/SVG-noise (software renderer); ~2 min per 32s short

scripts/tts-words.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+"""TTS with per-sentence timing (karaoke captions).
+
+Usage: tts-words.py <text> <voice> <out.mp3> <out.sentences.json>
+Writes mp3 + JSON [{w, start, end}] (seconds, relative to segment start).
+Uses edge-tts SentenceBoundary stream events.
+"""
+import asyncio
+import json
+import sys
+
+import edge_tts
+
+
+async def main(text: str, voice: str, mp3_path: str, sentences_path: str) -> None:
+    comm = edge_tts.Communicate(text, voice)
+    sentences = []
+    with open(mp3_path, "wb") as f:
+        async for chunk in comm.stream():
+            if chunk.get("type") == "audio":
+                f.write(chunk.get("data", b""))
+            elif chunk.get("type") == "SentenceBoundary":
+                start = chunk.get("offset", 0) / 1e7
+                dur = chunk.get("duration", 0) / 1e7
+                sentences.append(
+                    {"w": chunk.get("text", ""), "start": round(start, 3), "end": round(start + dur, 3)}
+                )
+    with open(sentences_path, "w") as f:
+        json.dump(sentences, f)
+
+
+if __name__ == "__main__":
+    asyncio.run(main(sys.argv[1], sys.argv[2], sys.argv[3], sys.argv[4]))