video-gen: adopt Seedance 2.0 as preferred premium default

Seedance 2.0 is now routed as the top-ranked video generator whenever a
premium gateway is available. Touches the tool layer, scoring engine,
cinematic pipeline, and both skill layers so discovery works from every
entry point.

- tools/video/seedance_video: BETA stability, quality_score=0.95, add
  reference_to_video operation plus 9 img + 3 vid + 3 audio ceilings,
  fix pre-existing upload_image_fal import
- tools/base_tool: surface optional quality_score / success_rate /
  latency fields in get_info so the scorer can read them
- lib/scoring: fix reliability enum-vs-string bug that was pinning every
  available tool to 0.0, switch to overlap coefficient so rich best_for
  descriptions aren't penalized, add premium-cinematic feature bonus
- pipeline_defs/cinematic + cinematic asset-director: add pixabay_music
  and freesound_music, restore pixabay-first music default
- cinematic compose-director: mandatory Remotion preflight at stage entry
- New Layer 3 .agents/skills/seedance-2-0/SKILL.md (8-part prompt
  structure, multi-shot, lip-sync, reference-to-video, provider landscape)
- New Layer 2 skills/creative/prompting/seedance-prompting.md
- Update ai-video-gen, video-gen-prompting, AGENT_GUIDE, INDEX to flag
  Seedance 2.0 as the preferred premium default and make the skill
  discoverable from every routing path

skills/pipelines/cinematic/asset-director.md

@@ -27,7 +27,7 @@ Before authoring title cards, name plates, or SVG overlays, read **`skills/meta/
 |-------|----------|---------|
 | Schema | `schemas/artifacts/asset_manifest.schema.json` | Artifact validation |
 | Prior artifacts | `state.artifacts["scene_plan"]["scene_plan"]`, `state.artifacts["script"]["script"]`, `state.artifacts["proposal"]["proposal_packet"]` | Scene intent and beat plan |
-| Tools | `subtitle_gen`, `audio_enhance`, `image_selector`, `video_selector`, `music_gen` — selectors auto-discover all available providers from the registry | Optional support asset creation |
+| Tools | `subtitle_gen`, `audio_enhance`, `image_selector`, `video_selector`, `pixabay_music` (free, default), `freesound_music` (free), `music_gen` (ElevenLabs, paid) — selectors auto-discover all available providers from the registry. **Default to `pixabay_music` before reaching for `music_gen`.** | Optional support asset creation |
 | Playbook | Active style playbook | Brand and typography consistency |
 
 ## Process
@@ -54,7 +54,7 @@ If `proposal_packet.metadata.motion_required = true`, actual moving footage or g
 Before batch-generating support assets, produce one sample of each expensive generated type and show the user:
 
 1. **Generated insert sample** (if using `image_selector` or `video_selector`): Generate one representative visual. Confirm it complements the source footage before batching.
-2. **Music sample** (if using `music_gen`): Generate a short clip. Confirm mood and energy match the beat plan.
+2. **Music sample** (try `pixabay_music` first — free, searchable by mood/BPM; fall back to `freesound_music` for cues and ambience; only reach for `music_gen` when the search tools miss the brief): sample or retrieve a short clip. Confirm mood and energy match the beat plan.
 
 If `motion_required = true`, the representative visual must be a video clip sample, not a still image sample.
 

skills/pipelines/cinematic/compose-director.md

@@ -24,6 +24,20 @@ If the approved brief or scene plan makes motion a hard requirement, verify that
 - Do not convert the piece into an animatic unless the user explicitly approves that downgrade.
 - If the render engine changes materially, tell the user before rendering and explain why.
 
+**Mandatory Remotion preflight (run before every render when the scene plan includes any Remotion scene type — title cards, stat cards, anime/hero_title, end-tag, overlays):**
+
+```bash
+python -c "
+from tools.tool_registry import registry
+registry.discover()
+info = registry.get('video_compose').get_info()
+print('Render engines:', info.get('render_engines'))
+print('Remotion note:', info.get('remotion_note'))
+"
+```
+
+If Remotion is not in the available render engines, stop and report to the user per the Decision Communication Contract. Do not substitute a reduced-fidelity render path without approval.
+
 ### 1. Use Frame Treatment Deliberately
 
 Only use letterbox, 24fps intent, or heavy grading if they help the piece. Do not apply them because the pipeline name says cinematic.