Timeline panel default height is too tall (50% of editor)

[MeepCastana]

Problem

The timeline panel opens taking 50% of the editor height by default. That is far more than a new project needs — an empty or short timeline shows mostly blank track area while the preview, the thing the user is actually looking at, is squeezed into the other half.

Cause

// src/shared/state/editor-panel-layout-store.ts:18-24
const DEFAULT_PANELS: EditorPanelSizes = {
  tools: 25,
  preview: 50,
  properties: 25,
  mainContent: 50,
  timeline: 50,
};

mainContent: 50 / timeline: 50 splits the editor shell evenly. Consumed at src/features/editor/components/editor.tsx:485 and :626.

The panel constraints allow much more room to breathe:

// src/features/editor/components/editor.tsx:626-629
<ResizablePanel defaultSize={panels.timeline} minSize={15} maxSize={70}>

Suggested fix

Lower the default to somewhere in the 28–35% range and raise mainContent to match, so the two still sum to 100.

Two things to be careful about:

1. The store is persisted. Anyone who has already opened the editor has timeline: 50 written to storage, so changing DEFAULT_PANELS alone will not affect existing users. Decide whether that's acceptable (new users only) or whether this needs a store version bump / migration.

2. resetPanels() exists at editor-panel-layout-store.ts:43 — worth confirming it's reachable from the UI so users can get back to the new default.

Also worth a look: src/features/editor/components/editor.test.tsx:171 and :263 hardcode timeline: 50 and timelineDefaultSize: 35. Those two numbers already disagree with each other; whoever picks this up should reconcile them.

Acceptance criteria

• A new user opening the editor for the first time sees a timeline noticeably shorter than half the screen
• Panel sizes still sum to 100
• Timeline remains resizable across the full minSize={15} – maxSize={70} range
• Decision documented in the PR on whether existing persisted layouts are migrated or left alone
• npm run lint and npm run test:run pass

Good first issue — one constant, but read the persistence note first.