hyperframes: add HTML/CSS/GSAP as a parallel composition runtime

Separates creative grammar (renderer_family) from technical engine
(render_runtime) so HyperFrames can stand alongside Remotion as a
first-class runtime instead of masquerading as a Remotion sub-case.
Locks runtime choice at proposal stage and enforces it end-to-end: the
schemas require it, video_compose routes by it, the reviewer fails
closed on silent swaps, and a parametrized contract test walks every
pipeline manifest to ensure each planning-stage skill explains the
conversation to the user. Adds hyperframes_compose (scaffold/lint/
validate/render/doctor/add_block), a playbook -> CSS style bridge, and
vendored HyperFrames Layer 3 skills from commit d291358, pinned via
PROVENANCE.md for future re-sync. Final_review now records
render_runtime_used and runtime_swap_detected so compose lies are
catchable after the fact.

skills/creative/animation-pipeline.md

@@ -1,8 +1,27 @@
 # Animation & Motion Graphics Pipeline
 
 > Sources: School of Motion curriculum, After Effects documentation, Remotion documentation,
-> Disney's 12 Principles of Animation (Frank Thomas & Ollie Johnston), Motion Design School,
-> The Animator's Survival Kit (Richard Williams)
+> HyperFrames documentation, Disney's 12 Principles of Animation (Frank Thomas & Ollie
+> Johnston), Motion Design School, The Animator's Survival Kit (Richard Williams)
+
+## Runtime Choice — Remotion vs HyperFrames
+
+Animation work in OpenMontage runs on one of two composition runtimes. Both
+are first-class; the choice is creative, not a fallback:
+
+- **Remotion (React-based)** — when the scene is a React component, uses the
+  existing chart/text-card/comparison/kpi stack, or needs pixel-accurate
+  frame-level interpolation through `useCurrentFrame()` + `interpolate()`.
+  Default for data-heavy explainers.
+- **HyperFrames (HTML/GSAP)** — when the motion is expressed naturally as
+  CSS + GSAP timelines: kinetic typography, product promos, launch reels,
+  website/UI-driven compositions, registry-block-driven scenes. Default
+  when the brief is motion-graphics-led and the scene library in
+  `remotion-composer/` doesn't already cover the look.
+
+See `skills/core/hyperframes.md` and `skills/meta/animation-runtime-selector.md`
+for the full decision matrix. Whichever runtime is chosen at proposal must
+be locked in `edit_decisions.render_runtime` and preserved through compose.
 
 ## Quick Reference Card