Visor: persistent drawer action bar above the strip

[lannbot]

Summary

• Add a non-scrolling action bar directly above the strip, inside the existing drawer height budget.
• Show Close on clean dismissible sheets; replace it with Save and Revert when settings or app-label drafts are modified.
• Keep Save/Revert in the current sheet. Preserve existing unsaved-navigation confirmation, and omit actions on the pinned app list and unlock screen as requested.
• Remove the pane-top dismissal and inline settings Save/Revert controls they replace.
• Guard in-flight saves against duplicate submission/navigation, preserve newer edits, and keep keyboard focus on a useful control without stealing it from ongoing typing.

Verification

• Astra review complete; real Chromium desktop/mobile clean and dirty screenshots inspected.
• just check passed.
• just test passed, including 36 Deno tests.
• just e2e passed: 29 scenarios, including contrast/touch coverage.
• Behavioral coverage checks persistence, Revert, app-label saves, pinned screens, keyboard focus, in-flight edits/navigation, confirmation, and the bar remaining attached after pane scrolling and mobile resize.

Automerge will be armed.