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)

AGENT_GUIDE.md

@@ -616,6 +616,11 @@ Tool rules:
 | `clean-professional` | Corporate, educational, SaaS |
 | `flat-motion-graphics` | Social media, TikTok, startups |
 | `minimalist-diagram` | Technical deep-dives, architecture |
+| `ink-sketch` (Ink Theater) | Hand-drawn ink-on-white doodle animation; a character that draws itself, walks, dances; contraption explainers |
+
+### Hand-drawn "doodle" animation → Ink Theater / Ink Puppet
+
+For any brief that wants a **hand-drawn ink doodle** look — "a sketch that comes to life", "a pencil / stick figure that walks or dances", "a little character that acts out the idea", whiteboard-doodle explainers — use the **Ink Theater** engine + **Ink Puppet** mocap system (`skills/creative/ink-theater.md`, `ink-theater/README.md`). It is a **style + reusable engine, not a new pipeline**: illustration / contraption pieces run on the `animation` pipeline; a mocap character (draws itself → walks / dances / waves via `InkPuppet.choreograph([...])`) runs on `character-animation`. Cross-tool entry points: **`/ink-art`** (create a vector doodle from scratch) and **`/animated-drawing`** (animate a *supplied* drawing with mocap — raster; `skills/creative/animated-drawing.md`). Never hand-tune character motion — the agent only chooses named mocap clips.
 
 ## Layer Map