fix(project drawer)project rail drawer toggle

[suntianc]

Summary

• Fix the project rail drawer toggle so clicking the double-chevron again closes the drawer.
• Add a regression test for the open-then-close interaction.

Root Cause

The drawer listens for outside clicks on mousedown. When the drawer was open, clicking the rail toggle first triggered that outside-click handler, closing the drawer, then the button click handler toggled it open again.

Validation

• pnpm lint
• pnpm test
• pnpm build