feat(desktop): enable multi-window support and new window action (#377)

* feat(macos): add New Window menu item

Add a New Window option to the macOS menu bar
Trigger opening a separate window when the New Window action is selected

* feat: enable multiple desktop windows and new window shortcut

Enable multiple desktop windows by extending manifest to main-*
Expose desktop_new_window to create additional windows from UI
Show New Window shortcut in Help dialog (Desktop only) with Shift + Alt + <mod> + N

* feat(desktop): enable opening host URL in new window from host switcher

Add a new action to launch a URL in a separate window from the host switcher
Wire the UI to open the selected host in a new window using a dedicated control
Expose a cross-platform API to create a new window pointing at a URL

* fix(desktop): validate URL scheme before opening new window

* fix(desktop): skip unreachable hosts when opening new windows

packages/desktop/src-tauri/capabilities/default.json

@@ -12,7 +12,7 @@
       "https://*/*"
     ]
   },
-  "windows": ["main"],
+  "windows": ["main", "main-*"],
   "permissions": [
     "core:default",
     "core:window:default",