✨ Full-text search across all tabs

[fusion94]

Description

Expand the current / search to query across all data sources (issues, PRs, tasks, notes, calendar events) — not just the active tab.

Current Behavior

The / shortcut filters cards within the current tab only. No cross-tab or global search.

Expected Behavior

• / opens a global search overlay (command-palette style)
• Results grouped by type: Issues, PRs, Tasks, Calendar, Notes
• Keyboard navigable (↑↓ to move, Enter to jump to item, Esc to close)
• Searches titles, labels, body text, and repo names
• Clicking a result navigates to the relevant tab and highlights the card
• Optional: fuzzy match support

Acceptance Criteria

• Global search overlay triggered by /
• Results from all data sources in a single view
• Grouped by type with counts
• Keyboard navigation works
• Selecting a result jumps to the right tab + highlights card
• Esc closes overlay