Single-owner window keydown action for the Transcribe panel: j/k region
nav, e mode toggle, n draw (edit only), t training mark, Delete, ? cheat-
sheet, and the Esc precedence ladder (cheatsheet → editable no-op → close
panel). Pure input-to-callback translator with a focus guard that exempts
only "?"; removes its listener on destroy. 20 unit tests cover every key,
the panel/focus guards, the Esc matrix, and teardown.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
When the bottom sheet closes, focus returns to the element that was focused
before it opened instead of being dropped to document.body (WCAG 2.4.3,
Architect + UX review).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Focuses the first focusable on mount and wraps Tab/Shift+Tab within the node.
Used by the Stammbaum mobile bottom sheet (NFR-A11Y-004).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
