Front end: LocalConsole marshal + single-binary loop (timed stop, relaunch)

The in-process console that replaces the operator for solo play: it owns
the mission clock and ends the race at the chosen length, then relaunches
to the setup menu -- the arcade launcher behavior in one binary.

- engine/APPMGR: gPerFrameHook -- a per-frame observer called on the game
  thread in RunMissions (the marshal's engine-safe tick site).
- btl4console.{hpp,cpp}: BTLocalConsole_Install/MissionCompleted -- the
  marshal watches for RunningMission, starts the clock, and dispatches
  Application::StopMissionMessage at expiry (BT_MISSION_SECONDS overrides
  for testing).  Confirmed: StopMission cleanly ends the mission and
  RunMissions returns.
- btl4fe: expose BTFrontEnd_LastMissionSeconds; Enter=LAUNCH / Esc=quit in
  the menu loop; BT_FE_AUTOLAUNCH quick-launch (skips the menu).
- btl4main WinMain: front-end mode runs menu -> arms marshal -> mission;
  when the marshal ends it, RELAUNCH a fresh instance (arcade launcher
  model) -> lands back on the menu.  This sidesteps BT's in-process
  re-init fragility: a second mission in-process AV'd on stale gBT*
  per-mission entity globals (gBTTerrainEntity et al., cdb-traced to
  MakeEntityRenderables); a fresh process has none.

Verified: menu LAUNCH -> mission runs -> marshal stops it at the set
length -> RunMissions returns -> relaunch (3 distinct PIDs across a
multi-cycle run, no crash).

Remaining in Phase 5: the results screen (kills/deaths at stop).

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

engine/MUNGA/APPMGR.cpp

@@ -12,6 +12,11 @@ HWND ghWnd = 0;
 // front end / lobby member path (Phase 5/6).
 Logical gConsoleLossEndsMission = False;
 
+// BT412: a per-frame observer called each frame in RunMissions while an
+// application is live (the in-process LocalConsole marshal hangs off this to
+// own the mission clock).  NULL when unregistered.
+void (*gPerFrameHook)() = NULL;
+
 ApplicationManager* ApplicationManager::CurrentAppManager = NULL;
 
 ApplicationManager::ApplicationManager(HINSTANCE hInstance, HWND hWnd, Scalar frame_rate) : Node(ApplicationManagerClassID), runningApplications(this)
@@ -81,6 +86,15 @@ Start_Of_Frame:
 	{
 		Check(application);
       foregroundTasksRun++;
+
+		//------------------------------------------------------------------
+		// BT412: give the per-frame observer a slice while 'application' is
+		// live (the loop condition NULLs the global on exit).  The
+		// single-player LocalConsole marshal hangs off this; NULL otherwise.
+		//------------------------------------------------------------------
+		if (gPerFrameHook != NULL)
+			(*gPerFrameHook)();
+
 		if (!application->ExecuteForeground(end_of_frame, frameDuration))
 		{
 			if (!application->Shutdown(current_application.GetSize()))