feat(studio): html-backed motion panel (#873)

## Summary

Re-architects the studio motion panel to persist GSAP motion data directly in HTML element attributes instead of a `.hyperframes/studio-motion.json` JSON sidecar file. Same pattern as position/resize/rotation edits.

### Before
```
MotionPanel → commitStudioMotionManifestOptimistically()
  → writes .hyperframes/studio-motion.json
  → applyStudioMotionManifest(doc, manifest)
```

### After
```html
<div id="hero" data-hf-studio-motion='{"start":0.5,"duration":1,"ease":"power3.out","from":{"opacity":0,"y":40},"to":{"opacity":1,"y":0}}'>
```
```
MotionPanel → writeStudioMotionToElement(element, motion)
  → buildMotionPatches(element)
  → commitPositionPatchToHtml(selection, patches)
```

## What changed

- **studioMotionOps.ts** — Added `readStudioMotionFromElement()`, `writeStudioMotionToElement()`, `clearStudioMotionFromElement()` for attribute-based CRUD
- **studioMotion.ts** — Added `applyStudioMotionFromDom()` that reads motion from DOM attributes and builds GSAP timeline (kept `applyStudioMotionManifest` for render script compat)
- **manualEditsDom.ts** — Added `buildMotionPatches()` / `buildClearMotionPatches()`, integrated motion into `reapplyPositionEditsAfterSeek()`
- **useDomEditCommits.ts** — Rewrote `handleDomMotionCommit` / `handleDomMotionClear` to use HTML patching instead of manifest persistence
- **useManifestPersistence.ts** — Removed all motion manifest state (~200 lines): `studioMotionManifestRef`, `commitStudioMotionManifestOptimistically`, `applyStudioMotionToPreview`, motion SSE handler
- **App.tsx** — Reads motion from element attribute (`readStudioMotionFromElement`) instead of manifest ref
- **manualEditsRenderScript.ts** — Extended `studioPositionSeekReapplyRuntime` to rebuild GSAP motion timeline from `data-hf-studio-motion` attributes after each seek, including CustomEase support
- **htmlCompiler.ts** — Trigger seek-reapply script injection on `data-hf-studio-motion=` attributes

## Benefits

- No sidecar file — motion survives git, copy-paste, and manual HTML editing
- Undo/redo works via HTML source history (same as position edits)
- Renders correctly via CLI — seek-reapply script handles motion timeline rebuild
- Simpler architecture — one persistence path for all studio edits

## Test plan

- [x] `bun run build` passes
- [x] Pre-commit hooks pass (lint, format, typecheck)
- [ ] Set motion on element in Studio → `data-hf-studio-motion` attribute appears in HTML source
- [ ] Reload page → motion persists and plays correctly
- [ ] Clear motion → attribute removed, element returns to original state
- [ ] Undo/redo motion changes
- [ ] Render via CLI → motion visible in rendered video
- [ ] Seek animation → motion timeline re-syncs correctly

packages/studio/src/components/editor/MotionPanel.tsx

@@ -24,14 +24,14 @@ import {
 } from "./MotionPanelFields";
 import { EaseCurveEditor } from "./EaseCurveEditor";
 
+/** Motion data without targeting metadata (kind/target/updatedAt are derived from context). */
+type StudioMotionData = Omit<StudioGsapMotion, "kind" | "target" | "updatedAt">;
+
 interface MotionPanelProps {
   element: DomEditSelection | null;
-  motion: StudioGsapMotion | null;
+  motion: StudioMotionData | null;
   onClearSelection: () => void;
-  onSetMotion: (
-    element: DomEditSelection,
-    motion: Omit<StudioGsapMotion, "kind" | "target" | "updatedAt">,
-  ) => void;
+  onSetMotion: (element: DomEditSelection, motion: StudioMotionData) => void;
   onClearMotion: (element: DomEditSelection) => void;
 }
 
@@ -43,19 +43,19 @@ const MOTION_PRESET_OPTIONS: Array<{ label: string; value: StudioGsapMotionPrese
 
 const MOTION_DIRECTION_OPTIONS: StudioGsapMotionDirection[] = ["up", "down", "left", "right"];
 
-function motionValueDistance(motion: StudioGsapMotion | null): number {
+function motionValueDistance(motion: StudioMotionData | null): number {
   if (!motion) return 32;
   return Math.max(Math.abs(motion.from.x ?? 0), Math.abs(motion.from.y ?? 0), 1);
 }
 
-function inferMotionPreset(motion: StudioGsapMotion | null): StudioGsapMotionPreset {
+function inferMotionPreset(motion: StudioMotionData | null): StudioGsapMotionPreset {
   if (!motion) return "fade-up";
   if (motion.from.scale != null || motion.to.scale != null) return "pop";
   if (motion.from.x != null || motion.to.x != null) return "slide";
   return "fade-up";
 }
 
-function inferMotionDirection(motion: StudioGsapMotion | null): StudioGsapMotionDirection {
+function inferMotionDirection(motion: StudioMotionData | null): StudioGsapMotionDirection {
   if (!motion) return "up";
   const x = motion.from.x ?? 0;
   const y = motion.from.y ?? 0;