feat(character-animation): add local rigged character pipeline

New beta pipeline for reusable cartoon characters with SVG rigs, pose
libraries, action timelines, and Canvas/Remotion/HyperFrames rendering.

- pipeline_defs/character-animation.yaml: 11-stage manifest
- skills/pipelines/character-animation/: 11 stage director skills
- tools/character/: BaseTool implementations for char design, rigging,
  pose libraries, action timelines, previews, and QA
- schemas/artifacts/{character_design,rig_plan,pose_library,
  action_timeline,character_qa_report}.schema.json: canonical artifacts
- schemas/artifacts/scene_plan.schema.json: extended for character-led
  scenes
- .agents/skills/{canvas-procedural-animation,character-animation-qa,
  character-rigging,pose-library-design,svg-character-animation}/:
  Layer 3 vendor knowledge
- AGENT_GUIDE / PROJECT_CONTEXT / README / ARCHITECTURE / PROVIDERS:
  surface the new pipeline and its capability family
- tools/video/hyperframes_compose.py: SVG character rig support
- tests/contracts/test_character_animation_pipeline.py: contract tests

.agents/skills/character-rigging/SKILL.md

@@ -0,0 +1,53 @@
+---
+name: character-rigging
+description: Build data-driven 2D character rigs for local animation: parts, pivots, layers, constraints, views, and reusable rig packages.
+license: MIT
+---
+
+# Character Rigging
+
+Use this skill when building OpenMontage `rig_plan` artifacts or renderer input
+for local 2D character animation.
+
+## Proven Patterns
+
+- Keep runtime code generic; make each character a data package.
+- Split characters into independently transformable parts.
+- Define pivots in the same coordinate space as the artwork.
+- Store constraints on moving parts to prevent impossible rotations.
+- Keep layer order explicit; do not rely on SVG source order after generation.
+- Start with one view and add views only when the shot list requires them.
+
+## Rig Package
+
+```json
+{
+  "character_id": "mouse",
+  "rig_type": "svg_rig",
+  "parts": [
+    { "id": "body", "kind": "torso", "layer": 10 },
+    { "id": "head", "kind": "head", "layer": 30, "parent": "body" },
+    { "id": "arm_right", "kind": "limb", "layer": 40, "parent": "body" }
+  ],
+  "joints": {
+    "head": { "pivot": [320, 180], "rotation": [-20, 20] },
+    "arm_right": { "pivot": [390, 310], "rotation": [-70, 95] }
+  }
+}
+```
+
+## Quality Checklist
+
+- Every moving part has a pivot.
+- Every child part has a parent where hierarchy matters.
+- Mouth shapes are separate assets or separate path groups.
+- Eyes and pupils are separate when gaze needs to change.
+- Props are separate if the character touches or carries them.
+
+## Sources
+
+- SVG transform-origin behavior is browser-defined and can be sensitive to
+  coordinate space; prefer explicit SVG-coordinate pivots when using GSAP
+  `svgOrigin`: https://gsap.com/docs/v3/GSAP/CorePlugins/CSS/
+- Remotion animations must be frame-driven and deterministic via current frame:
+  https://www.remotion.dev/docs/use-current-frame