fix: improve menu bar styling for active states and opacity
- Unify hover and current app states to use consistent 5% black tint
- Layer tint over facet background in collapsed mode for visibility
- Make expanded sidebar fully opaque to prevent content bleed-through
- Remove font-weight change for current app in favor of background tint
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>