Restore thread title tooltip in sidebar

[UtkarshUsername]

Summary

• Restore the full thread title as the title attribute on sidebar thread rows.
• Suppress the tooltip while a thread is being renamed so the inline edit flow is not interrupted.
• Add a browser test covering the sidebar row tooltip behavior.

Testing

• bun fmt
• bun lint
• bun typecheck
• Added/updated browser test: verifies the sidebar thread row exposes the full thread title via title.