feat: discoverability + cross-agent slash commands for Ink Theater / Animated Drawing

Makes the doodle-animation capability findable instead of hidden.

Routing (OpenMontage-internal):
- AGENT_GUIDE: Style Playbooks gets an ink-sketch row + a 'hand-drawn doodle'
  routing note (it's a style + engine on the animation / character-animation
  pipelines, NOT a new pipeline).
- animation/idea-director + character-animation/character-design-director point
  to the Ink Theater / Ink Puppet skills for hand-drawn character briefs.

Cross-agent slash commands (/ink-art, /animated-drawing) for Claude Code,
Copilot, Cursor, and Codex — thin pointers to the canonical skills so they stay
in sync. /ink-art = create a vector doodle from scratch (Ink Theater + Ink
Puppet mocap); /animated-drawing = animate a SUPPLIED drawing via Meta
AnimatedDrawings (raster). New skills/creative/animated-drawing.md documents the
Path A setup/run/limits. Codex prompts are user-home only — .codex/prompts/README
explains the copy/symlink step.

  .claude/commands/*.md            (Claude Code)
  .github/prompts/*.prompt.md      (Copilot)
  .cursor/commands/*.md            (Cursor)
  .codex/prompts/*.md + README     (Codex; copy to ~/.codex/prompts)

.codex/prompts/README.md

@@ -0,0 +1,12 @@
+# Codex custom prompts
+
+Codex only scans **`~/.codex/prompts/`** (user home) for custom prompts — it does **not** read project-level `.codex/prompts/`. These files are versioned here as the source of truth; to use them in Codex, copy or symlink them into your home dir:
+
+```bash
+mkdir -p ~/.codex/prompts
+cp .codex/prompts/ink-art.md .codex/prompts/animated-drawing.md ~/.codex/prompts/
+# or symlink so repo edits propagate:
+# ln -s "$PWD/.codex/prompts/ink-art.md" ~/.codex/prompts/ink-art.md
+```
+
+Then restart Codex; `/ink-art` and `/animated-drawing` appear in the `/` menu. (OpenAI is deprecating custom prompts in favor of Codex "skills" — migrate when that stabilizes.)

.codex/prompts/animated-drawing.md

@@ -0,0 +1,12 @@
+---
+description: Animate a SUPPLIED drawing/photo with real mocap (Meta AnimatedDrawings) → raster GIF/MP4. To create a vector doodle from scratch, use /ink-art.
+argument-hint: [path to drawing] [motion: dance|walk|jump|wave]
+---
+
+Read `skills/creative/animated-drawing.md`, then set up and run Meta's open-source AnimatedDrawings to animate the supplied drawing with the requested motion.
+
+- Only for animating an *existing* humanoid drawing/photo. To create a vector doodle from scratch → use `/ink-art`.
+- Output is **raster** (original drawing warped) — no vector, no draw-on reveal.
+- Prefer the turnkey bundled-character path; auto-rig needs Docker + ~670 MB models.
+
+Drawing + motion: $ARGUMENTS

.codex/prompts/ink-art.md

@@ -0,0 +1,12 @@
+---
+description: Hand-drawn ink doodle animation — a character that draws itself then walks/dances/waves, or a contraption explainer (vector → HyperFrames MP4).
+argument-hint: [what to animate]
+---
+
+Read `skills/creative/ink-theater.md` and `ink-theater/README.md`, then build the hand-drawn ink animation described below.
+
+- **Ink Theater** engine (`ink-theater/ink-theater.js`): variable-width ink strokes, seek-safe boil, closed-form spring eases, FABRIK IK, contraption grammar.
+- For a **character that walks / dances / waves / jumps**, use the **Ink Puppet** mocap system: `InkPuppet.create` → `p.drawIn` (self-drawing reveal) → `InkPuppet.choreograph([{clip:'wave_hello'},{clip:'dab'},…])`. **Never hand-tune motion**; add moves via `ink-theater/mocap/bvh2clip.mjs`.
+- Captions = **HTML overlay `<div>`s** (HyperFrames doesn't apply webfonts to SVG `<text>`). Validate (`npx hyperframes lint` + `snapshot`) before rendering.
+
+Request: $ARGUMENTS