refactor(skills): rebuild faceless-explainer + pr-to-video on the shot-sequence architecture (#1778)

* refactor(skills): rebuild faceless-explainer + pr-to-video on the shot-sequence architecture

Move both skills onto the current shot-sequence authoring architecture and
the latest shared engine, then re-narrate to each domain. The engine fixes
(pre-assembly frame guards + BGM loop-extend in assemble-index, dark-ground
caption contrast, brand-accent selection + mono role in tokens, dark-mode
polarity invert / weight-clamp / icon-font filter in build-frame) had only
landed in one copy; both skills were a generation behind.

- Authoring model: visual-design now writes a time-coded shot sequence (Scene
  windows paced to the voiceover) instead of the older effects-id phased note;
  motion-language carries the move vocabulary + the tightened motion doctrine
  (smooth over bouncy) + the seek-safe core (fromTo entrances, no CSS-transition
  motion); add cut-catalog (within-frame velocity-matched seams); frame-worker
  and SKILL Step 4/5 move to blueprint instantiation + shot-sequence fidelity.
- faceless-explainer: fold the standalone composition.md into visual-design
  (inventing-the-visual / portrait / caption geometry); keep the explainer
  story doctrine; graft cue-segmented VO + candidate-blueprint-from-Step-3.
- pr-to-video: keep the ingest pipeline (fetch-pr / ingest / fetch-people-avatars)
  and code-vocabulary; preserve the code-beat (code-* block as focal, Scenes
  choreograph the surround) and mechanism-beat treatments under the new model.
- Drop stage-assets from both (no captured assets to stage); remove derivation
  references so each skill reads standalone.

bun run scripts/lint-skills.ts passes; all scripts node --check clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore(skills): resync skills-manifest after format pass

The pre-commit skills-manifest hook hashed the skills before the format hook
reformatted cut-catalog.md, so the committed manifest lagged the on-disk
content and CI's "Skills: manifest in sync" check failed. Regenerated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

skills/pr-to-video/scripts/lib/dimensions.mjs

@@ -1,4 +1,4 @@
-// dimensions.mjs — canvas size + caption-band geometry for the product-launch
+// dimensions.mjs — canvas size + caption-band geometry for the video
 // pipeline. Single source of truth = the STORYBOARD frontmatter `format` global
 // ("1920x1080" / "1080x1920" / "1080x1080", or a named orientation). Every
 // script and the index assembler reads the size from here; none hardcodes it.