ie-shell: interactive chrome overlays — navigate tab list, bookmarks, address bar completion

[thomasnemer]

Goal

Make the browser chrome overlays interactive via keyboard navigation:

Tab list overlay (Ctrl+Shift+T)

• Up/Down arrow to highlight tabs
• Enter to switch to highlighted tab
• Delete to close highlighted tab
• Show active tab indicator

Bookmarks overlay (Ctrl+Shift+B)

• Up/Down arrow to highlight bookmarks
• Enter to navigate to highlighted bookmark URL
• Delete to remove highlighted bookmark

Address bar (Ctrl+L)

• Already works for typing and Enter to navigate
• Missing: show loading state while navigating
• Missing: show error state if navigation fails

General

• All overlays dismiss with Escape (already works)
• Visual feedback: selected item highlight in overlays

Current state

• Keyboard shortcuts trigger overlays and they render visually (Step 6d: Browser chrome overlay rendering #78)
• Tab/bookmark state management works (Step 4: ie-shell — Navigation service and tab model #7)
• But overlays are display-only — no keyboard navigation within them

Acceptance Criteria

• Can switch tabs using the tab list overlay
• Can navigate to a bookmark from the bookmarks overlay
• Arrow keys work within overlays