Add OverviewMenu escape menu, remove Tab mode cycling

- New OverviewMenu component: Esc toggles the pause overlay, buttons
  switch modes via GameModeManager.TrySwitchTo<T>() and close the panel;
  visibility follows the role-scoped mode set, active mode disabled.
- Esc in paint mode exits to camera mode instead (PlayerControlMode,
  hunter falls back to FirstPersonMode) rather than opening the menu.
- Centralized all Esc handling in OverviewMenu (browser close included)
  to avoid frame races; OnlineSessionBrowserUI gains IsOpen/Open/Close.
- GameModeManager: switchKey Tab-cycle removed, TrySwitchTo<T> added.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/Scripts/Components/UI/OverviewMenu.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: 6fff96a0af7faf3458af1fef51f6f4a0