feat(studio): redesign left panel — Code tab, Renders header, Lint bottom (#141)

## Summary

Major layout redesign matching the Paper mockup. The Code editor moves to the left panel, Renders moves to the header, and interactions are simplified.

## Layout changes

| Before | After |
|---|---|
| Left: Compositions \| Assets | Left: **Code** \| Compositions \| Assets |
| Right: Code \| Renders tabs | Right: Renders-only (hidden by default) |
| Header: Projects ← / Lint / panel toggles | Header: title / sidebar toggle / **Renders button** |
| Lint: header button | Lint: **pinned to bottom** of left panel |

## Interaction changes

- **Renders panel** opens via a dedicated header button (teal when active), hidden by default
- **ExpandOnHover removed** — replaced with inline autoplay on thumbnails:
  - Compositions: hover shows a tiny iframe (1920px scaled to 80px, 300ms debounce)
  - Assets: hover shows `<video autoPlay muted loop>` in the thumbnail cell
- **Deleted** `ExpandOnHover.tsx` (194 lines) and `ExpandedVideoPreview.tsx` (35 lines)
- **Left panel max width**: 50% viewport, auto-expands to 50% when opening a file in Code tab

## Visual polish

- Equal-width tabs (Code \| Compositions \| Assets)
- Sidebar toggle button highlighted when panel is open
- Phosphor duotone file-type icons (`FileHtml`, `FileCss`, `FileJs`, `FileTs`, etc.)
- "FILES" header removed from file tree
- Redundant "RENDERS (N)" title removed from renders panel

🤖 Generated with [Claude Code](https://claude.com/claude-code)

packages/studio/src/components/renders/RenderQueue.tsx

@@ -63,11 +63,8 @@ export const RenderQueue = memo(function RenderQueue({
 
   return (
     <div className="flex flex-col h-full">
-      {/* Header */}
-      <div className="flex items-center justify-between px-3 py-2 border-b border-neutral-800/50 flex-shrink-0">
-        <span className="text-[11px] font-medium text-neutral-500 uppercase tracking-wider">
-          Renders ({jobs.length})
-        </span>
+      {/* Header — no title, already shown in header button */}
+      <div className="flex items-center justify-end px-3 py-2 border-b border-neutral-800/50 flex-shrink-0">
         <div className="flex items-center gap-1.5">
           {completedCount > 0 && (
             <button