skills: adopt GSAP Layer 3 + Layer 2 animation-runtime routing

Mirror the official GSAP AI skills (greensock/gsap-skills, MIT) into
.agents/skills/ and add the Layer 2 wiring that makes them discoverable
from a fresh context.

GSAP covers animation needs that Remotion primitives strain at:
per-character text reveals (SplitText), SVG shape morphs (MorphSVG),
curved camera paths (MotionPath), stroke-reveal line drawing (DrawSVG),
layout-to-layout flight (Flip), and custom bezier easings (CustomEase).
Also becomes mandatory day-1 knowledge if we wire in HyperFrames later
(HF uses GSAP timelines as its native animation runtime).

Layer 3 adds (.agents/skills/):
- gsap-core, gsap-timeline, gsap-plugins, gsap-utils
- gsap-react, gsap-performance
- gsap-scrolltrigger, gsap-frameworks (situational)
- gsap/README.md — OpenMontage-specific framing and Remotion-safe usage

Layer 2 wiring (the discovery triggers):
- skills/meta/animation-runtime-selector.md — NEW routing meta-skill.
  Decision matrix covering Remotion primitives, GSAP plugins, framer-
  motion, Lottie, Manim, D3, TerminalScene. Enforces the "keep it
  simple" bias: reach for GSAP only when the plugin genuinely earns
  its bundle weight.
- skills/pipelines/explainer/asset-director.md — references GSAP for
  kinetic typography, multi-step choreography, SVG line draws.
- skills/pipelines/animation/asset-director.md — references GSAP for
  logo morphs, motion paths, FLIP transitions, custom easings.
- skills/pipelines/cinematic/asset-director.md — references GSAP for
  cinematic camera moves, per-char title reveals, prestige easings.
- AGENT_GUIDE.md — adds a categorized Layer 3 skills table so a fresh-
  context agent can find the right skill by what they're trying to do,
  plus a pointer to animation-runtime-selector.md for routing.

Determinism: every GSAP use inside Remotion must drive timeline progress
from useCurrentFrame(), never requestAnimationFrame. Three Remotion-safe
patterns are documented in both the gsap/README and the selector skill.

Attribution: https://github.com/greensock/gsap-skills (MIT).

skills/pipelines/animation/asset-director.md

@@ -4,6 +4,27 @@
 
 This stage prepares the actual animated ingredients: narration, diagrams, math renders, motion backgrounds, code visuals, and reusable type or layout systems.
 
+## Animation authoring — which runtime
+
+Before authoring motion-graphics components, read **`skills/meta/animation-runtime-selector.md`** for runtime routing. Animation is the pipeline most likely to justify GSAP plugins — logo morphs, curved camera paths, kinetic type, FLIP transitions.
+
+Quick routing for common animation-pipeline needs:
+
+| Motion type | Recommended approach |
+|---|---|
+| SVG logo morph between two shapes | GSAP MorphSVG — read `.agents/skills/gsap-plugins/SKILL.md` |
+| Line drawing / stroke reveal on SVG | GSAP DrawSVG — read `.agents/skills/gsap-plugins/SKILL.md` |
+| Object following a curved path | GSAP MotionPath — read `.agents/skills/gsap-plugins/SKILL.md` |
+| Per-character / per-word title reveals | GSAP SplitText — read `.agents/skills/gsap-plugins/SKILL.md` |
+| Custom bezier or elastic easing | GSAP CustomEase — read `.agents/skills/gsap-plugins/SKILL.md` |
+| Layout-to-layout element flight (FLIP) | GSAP Flip — read `.agents/skills/gsap-plugins/SKILL.md` |
+| Multi-step sequence across many elements | GSAP timeline — read `.agents/skills/gsap-timeline/SKILL.md` |
+| Particle overlay / background motion | Remotion `ParticleOverlay` component (already exists) |
+| Mathematical animation (graphs, equations) | Manim — read `.agents/skills/manim-composer`, `.agents/skills/manimce-best-practices` |
+| Ghibli / anime-style still-driven scene | Remotion `AnimeScene` component + FLUX image gen |
+
+**Remotion determinism rule:** every GSAP use inside a Remotion component must drive timeline progress from `useCurrentFrame()` — never `requestAnimationFrame`. Pattern examples in `.agents/skills/gsap-react/SKILL.md`.
+
 ## Prerequisites
 
 | Layer | Resource | Purpose |