feat(studio): use @hyperframes/player web component for preview (#238)

## Summary

- **Replaces the studio's hand-rolled iframe + scaling in** **`Player.tsx`** with the `<hyperframes-player>` web component, eliminating duplicated ResizeObserver, dimension detection, and stage-size message handling
- **Adds a public** **`iframeElement`** **getter** to the player web component so the studio's `useTimelinePlayer` can still access the inner iframe for clip manifest parsing, timeline probing, and DOM inspection
- **Updates player package exports** to resolve from source for workspace consumers (matching `@hyperframes/core` pattern), while npm-published consumers still get built `dist/` files

### Why a separate player package?

1. **Zero dependencies, any framework** — 12KB vanilla web component vs 940KB React+Zustand+CodeMirror studio
2. **CDN-ready** — single `<script>` tag, no build pipeline needed
3. **Embeddable by third parties** — users embed compositions in their own sites without the studio
4. **Single source of truth** — studio now uses the player instead of duplicating its scaling/detection logic

## Test plan

- [x] `pnpm --filter @hyperframes/player typecheck` passes
- [x] `pnpm --filter @hyperframes/studio typecheck` passes
- [x] `pnpm --filter @hyperframes/studio build` passes
- [x] `pnpm --filter @hyperframes/studio test` passes (2 pre-existing failures, unrelated)
- [x] E2E: Standalone player loads composition, detects 4s GSAP timeline, controls work, play/pause works
- [x] E2E: Studio preview renders via `<hyperframes-player>`, `iframeElement` bridge works, playback controls sync correctly

packages/player/package.json

@@ -11,11 +11,12 @@
     "dist"
   ],
   "type": "module",
-  "main": "./dist/hyperframes-player.js",
-  "types": "./dist/hyperframes-player.d.ts",
+  "main": "./src/hyperframes-player.ts",
+  "types": "./src/hyperframes-player.ts",
   "exports": {
     ".": {
-      "import": "./dist/hyperframes-player.js",
+      "types": "./src/hyperframes-player.ts",
+      "import": "./src/hyperframes-player.ts",
       "require": "./dist/hyperframes-player.cjs",
       "script": "./dist/hyperframes-player.global.js"
     }