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

tools/video/hyperframes_compose.py

@@ -1089,6 +1089,19 @@ class HyperFramesCompose(BaseTool):
 
         # Unknown cut shape — render a placeholder text card so the render
         # still succeeds; lint/validate will surface the issue.
+        if ext in {".html", ".htm"} and src_path:
+            rel = self._rel_from_workspace(str(src_path))
+            composition_id = Path(rel).stem
+            html = (
+                f'<div id="{cut_id}" class="clip composition-clip" '
+                f'data-composition-id="{self._escape_attr(composition_id)}" '
+                f'data-composition-src="{self._escape_attr(rel)}" '
+                f'data-start="{self._f(in_s)}" data-duration="{self._f(duration)}" '
+                f'data-width="{width}" data-height="{height}" '
+                f'data-track-index="1"></div>'
+            )
+            return html, None
+
         placeholder = self._escape_text(text or cut.get("reason") or f"Scene {index + 1}")
         html = (
             f'<div id="{cut_id}" class="clip text-card" '
@@ -1182,5 +1195,10 @@ class HyperFramesCompose(BaseTool):
         # If it's already a relative path starting with assets/, keep as-is.
         if not p.is_absolute():
             return str(p).replace("\\", "/")
+        parts = p.parts
+        for anchor in ("assets", "compositions"):
+            if anchor in parts:
+                index = len(parts) - 1 - list(reversed(parts)).index(anchor)
+                return "/".join(parts[index:])
         # Otherwise emit just the basename under assets/.
         return f"assets/{p.name}"