feat: Spotlight-like command palette

[vuon9]

Summary

This PR implements a Spotlight-like command palette that floats above all windows, including fullscreen apps on macOS.

Features

• Global Hotkey: Cmd+Ctrl+M (macOS) or Ctrl+Alt+M (Windows/Linux) opens the floating palette from anywhere
• macOS CollectionBehaviors:
  • CanJoinAllSpaces - appears on all virtual desktops
  • FullScreenAuxiliary - overlays fullscreen apps
  • Transient - temporary window behavior
• 27 Commands: Code formatters, converters, tools, data generators
• Fuzzy Search: Smart matching with scoring algorithm
• Recent Commands: Persists last 10 commands to localStorage
• Keyboard Navigation: Arrow keys, Enter, Escape
• Accessibility: ARIA attributes (role, aria-selected), focus management
• Carbon Design System: Uses Carbon tokens throughout

Technical Implementation

Backend (Go)

• service/spotlight.go - Spotlight window service
• main.go - Window creation with macOS behaviors, event handlers
• Event system for communication between spotlight and main windows

Frontend (React)

• SpotlightPalette component with fuzzy search
• Separate entry point (spotlight.jsx) for spotlight window
• Vite multi-entry configuration
• All new files follow Carbon Design System patterns

Testing

• Unit tests for spotlight service
• Manual testing guide at docs/spotlight-testing.md

Testing

1. Build: task build
2. Run: task run
3. Press Cmd+Ctrl+M to open spotlight
4. Type to search, arrow keys to navigate, Enter to select

Related

Closes #50

Commits

• feat(spotlight): add spotlight window service
• feat(spotlight): create spotlight window with macOS collection behaviors
• feat(spotlight): add spotlight window frontend components
• build(vite): configure spotlight entry point
• feat(spotlight): add navigation handling between spotlight and main window
• feat(spotlight): add macOS collection behaviors for spotlight window
• docs: add spotlight documentation and testing guide
• fix(spotlight): correct event name mismatch