fix: declare timeline three stdlib dependency

[catcherintheroad-hub]

Summary

• declare three-stdlib as a direct dependency of @aitube/timeline

Why

packages/timeline/src/components/controls/types.ts imports MapControls from three-stdlib, but packages/timeline/package.json does not declare three-stdlib directly. In my local validation this made packages/timeline declaration/build checks fail with:

src/components/controls/types.ts(1,48): error TS2307: Cannot find module 'three-stdlib' or its corresponding type declarations.

This is also relevant to the open timeline authoring work for #10 / PR #145 because the same missing direct dependency blocks packages/timeline build validation before the PR-specific code can be fully checked.

Validation

PATH=/opt/homebrew/opt/node@22/bin:$PATH bun run --cwd packages/timeline build

Passed locally after the dependency was declared.

No bounty claim; this is a small build unblocker for timeline review.