GPUI renderer: live AccessKit wiring, keyboard focus, and shortcuts

T065 delivered accessibility at the design-system/view-model layer (tested WCAG-AA contrast matrix, glyph+label statuses, accessible_label() / keyboard_shortcuts() data), but the live AccessKit wiring in the GPUI renderer is still pending.

Verified 2026-07-06 on macOS: probing the running app via the system accessibility tree exposes only window-chrome buttons (close/minimize/zoom) — none of the app content, nav, or controls.

Scope:

• Wire the existing accessible_label() data into the renderer's AccessKit tree (screens, nav, badges, buttons, terminal-surrounding controls).
• Keyboard navigation + visible focus states (design-brief §11).
• Shortcuts from the prototype: ⌘K palette, ⌘N start session, ⌘⇧L theme, ⌘[ back — plus session-switching and focus-terminal per the design brief (design/README.md "Keyboard shortcuts").

Refs: spec FR-009a, design-brief §11, tasks.md T065 note.

🤖 Generated with Claude Code

Start with design/README.md, especially the “Keyboard shortcuts” section and design-brief §11, then review the tasks.md T065 note and the existing accessible_label() data. Trace the GPUI renderer’s accessibility entry point and verify the running app’s system accessibility tree. Done means app screens, navigation, badges, buttons, and terminal controls appear there, with visible focus, keyboard navigation, and the listed shortcuts working.