fix(sim): wire btn_approve_script and expose pending_script_approval in hook API

_handle_approve_script existed but was not registered in the click handler dict.
_pending_dialog (PowerShell confirmation) was invisible to the hook API —
only _pending_ask_dialog (MCP tool ask) was exposed.

- gui_2.py: register btn_approve_script -> _handle_approve_script
- api_hooks.py: add pending_script_approval field to mma_status response
- visual_sim_mma_v2.py: _drain_approvals handles pending_script_approval

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gui_2.py

@@ -388,6 +388,7 @@ class App:
    'btn_mma_accept_tracks': self._cb_accept_tracks,
    'btn_mma_start_track': self._cb_start_track,
    'btn_approve_tool': self._handle_approve_tool,
+   'btn_approve_script': self._handle_approve_script,
    'btn_approve_mma_step': self._handle_approve_mma_step,
    'btn_approve_spawn': self._handle_approve_spawn,
   }