feat: global keyboard shortcut / hotkey support

Feature request

Global keyboard shortcuts — the ability to register system-wide hotkeys that trigger actions regardless of which app has focus.

Why this matters

This is table-stakes for many desktop app categories. Without it, zero-native apps are stuck as "browser tabs in a window frame" — they can only respond when the user tabs into them.

Real-world use cases

1. Gaming overlays (the one that made me notice this)

A League of Legends desktop assistant needs Shift+Tab to toggle an overlay showing live match data, champion stats, and post-game analysis — all while the user is in-game without alt-tabbing:

// What we do in Tauri today:
tauri_plugin_global_shortcut::Builder::new()
    .with_shortcut("Shift+Tab")
    .with_handler(|app, _shortcut, event| {
        // toggle overlay window visibility
    })
    .build()

2. Screenshot / clipboard tools
Ctrl+Shift+4 to capture a region, Ctrl+Shift+V to paste from history.

3. Quick launchers / search bars
Alt+Space to pop up an Alfred/PowerToys-style launcher.

4. Media / productivity apps
Play/pause, next track, mute mic — things users expect to work while typing in another app.

5. AI copilots / assistants
Ctrl+Shift+A to summon a floating chat window from anywhere.

What exists today (v0.2.0)

Scanned the codebase:

• TrayOptions / TrayItemId structs are declared in src/platform/root.zig but have zero implementation in any platform backend
• No global_shortcut or hotkey anywhere in src/, tools/, or skill-data/
• tauri-plugin-global-shortcut does not exist in the zero-native ecosystem

What makes this particularly important for zero-native

zero-native is targeting the Tauri replacement space. The top Tauri plugin by download count is tauri-plugin-global-shortcut. Every serious Tauri→zero-native migration hits this wall immediately.

The security model is actually a selling point here — shortcuts should be opt-in and policy-controlled just like the bridge, navigation, and everything else in app.zon:

.shortcuts = .{
    .{ .key = "Shift+Tab", .command = "toggle-overlay", .permissions = .{"window"} },
    .{ .key = "Ctrl+Shift+Space", .command = "quick-search" },
}

Platform APIs available

Platform	API
Windows	RegisterHotKey / UnregisterHotKey (Win32)
macOS	NSEvent.addGlobalMonitorForEventsMatchingMask or Carbon RegisterEventHotKey
Linux (X11)	XGrabKey
Linux (Wayland)	zwp_keyboard_shortcuts_inhibit_manager_v1 (protocol-dependent, may need portal)

Suggested scope

1. app.zon schema — a shortcuts array with key, command label, and optional permissions
2. Platform backend — register_hotkey / unregister_hotkey in the Platform vtable
3. Bridge integration — shortcut fires a window.zero event or invokes a registered bridge command
4. Platform support — start with Windows (RegisterHotKey is trivial) + macOS, Linux as follow-up

Happy to elaborate on any of these or help test — I have a real app waiting to migrate 😄

Start with the TrayOptions and TrayItemId declarations in src/platform/root.zig, then trace the Platform vtable and app.zon configuration model. Compare the Windows and macOS platform API requirements before deciding how registration reaches the bridge. Done means the schema, platform registration path, and shortcut-triggered window.zero event or bridge command are defined for the proposed platforms.