Polish note panels and context menu

- Fix context menu item padding caused by NSMenuItem state
- Fix floating toolbar icon spacing and alignment
- Add Cmd+Shift+D shortcut to delete active note
- Auto-focus text editor when opening a note
- Consolidate delete confirmation into WindowManager

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Fix release workflow: add contents write permission

GitHub Actions token needs explicit write permission to create releases
and upload assets.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Update menu bar icon to brain.head.profile SF Symbol

Replace note.text with brain.head.profile to match the app's
brain scraps identity.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>