Fix Remotion-first rendering docs and post-render verification gaps

Compose-director had contradictory instructions: Step 2 described Remotion
captions/audio, but Steps 5/5b gave detailed FFmpeg code that agents followed
instead. This caused three failures in production: FFmpeg subtitles instead of
Remotion CaptionOverlay, missing audio (mixed externally but never embedded in
Remotion props), and skipped audio verification in post-render review.

Changes:
- compose-director: Remotion is now DEFAULT for audio, captions, text overlays;
  FFmpeg is labeled FALLBACK only. Post-render review has mandatory ffprobe gate
  and audio transcription with explicit stop conditions.
- remotion.md: routing table updated (captions/audio → Remotion), added universal
  Post-Render Verification Protocol for all pipelines (only 2/10 had one).
- scene-director, asset-director: added pitfall for AI-generated text in CTA
  screens — must use Remotion text_card for verbatim text.
- image-provider-usage: added Recraft V4 caveat (style param causes 422 on fal.ai).
- recraft_image.py: documented the style parameter 422 issue inline.

tools/graphics/recraft_image.py

@@ -144,6 +144,14 @@ class RecraftImage(BaseTool):
         if inputs.get("image_size"):
             payload["image_size"] = inputs["image_size"]
         if inputs.get("style"):
+            # NOTE: As of 2026-04, fal.ai's Recraft V4 endpoint rejects the
+            # `style` parameter with a 422 Unprocessable Entity error. The
+            # style enum values (digital_illustration, realistic_image, etc.)
+            # are NOT accepted by the /fal-ai/recraft/v4/text-to-image route.
+            # Workaround: encode the style direction in the prompt text instead
+            # (e.g. "digital illustration of..." rather than style="digital_illustration").
+            # We still pass the parameter through in case fal.ai re-enables it,
+            # but callers should be aware this may fail.
             payload["style"] = inputs["style"]
         if inputs.get("colors"):
             payload["colors"] = inputs["colors"]