Join wait: animated waiting screen instead of "Not Responding"

The relay seat-wait loop (RelayRequestSeat -- the join/join_lan "patient
walk-up") blocked the window thread's message pump for its whole 30-minute
patience window: dial (2s timeout) -> Sleep(2000) -> repeat, with status
going only to the parent bat console.  Windows flagged the frozen game
window "Not Responding" until the operator started the session
(user-reported).

- BTWaitScreenPaint (L4VIDEO.cpp): a GDI waiting screen on the main window
  -- headline + detail line in the console green + a 12-segment marching
  spinner phased on the tick clock.  Pure GDI: flicker-free during the
  seat wait (no D3D presenting yet), and re-painted after each
  ExecuteIdle Present so the WaitingForEgg phase (previously a bare black
  frame) shows "WAITING FOR MISSION ASSIGNMENT" too.
- RelayWaitTick (L4NET.CPP): PeekMessage pump + paint.  The outer dial
  loop's Sleep(2000) becomes 20 pumped 100ms slices ("WAITING FOR THE
  OPERATOR'S SESSION" / "session at <ip:port> -- close this window to
  cancel"); the inner seat-reply wait pumps per 200ms select slice.

Verified live against a dead relay address: window-only PrintWindow capture
shows the animated screen, and user32 IsHungAppWindow (the API behind "Not
Responding") reports FALSE throughout the wait.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

engine/MUNGA_L4/L4NET.CPP

@@ -1506,6 +1506,24 @@ void L4NetworkManager::HostDisconnectedMessageHandler(HostDisconnectedMessage* H
 // relaySelf and everything downstream (egg self-match, HELLO) proceeds as if
 // BT_SELF had been set.  SEAT_FULL / timeout => False.
 //
+//
+// RelayWaitTick -- pump the window thread + paint the animated waiting screen
+// (join/join_lan UX fix 2026-07-22: the seat-wait loop blocked the message
+// pump for its whole 30-min patience window, so the main window showed "Not
+// Responding" until the console started the game).
+//
+static void RelayWaitTick(const char *line1, const char *line2)
+{
+	MSG msg;
+	while (PeekMessageA(&msg, NULL, 0, 0, PM_REMOVE))
+	{
+		TranslateMessage(&msg);
+		DispatchMessageA(&msg);
+	}
+	extern void BTWaitScreenPaint(const char *, const char *);
+	BTWaitScreenPaint(line1, line2);
+}
+
 Logical L4NetworkManager::RelayRequestSeat()
 {
 	//
@@ -1541,7 +1559,17 @@ Logical L4NetworkManager::RelayRequestSeat()
 			{
 				BTRelayWaitStatus("\n");
 			}
-			Sleep(2000);
+			{
+				char detail[128];
+				sprintf(detail, "session at %s:%d -- close this window to cancel",
+					inet_ntoa(relayGameAddress.sin_addr),
+					(int)ntohs(relayGameAddress.sin_port) - 1);
+				for (int slice = 0; slice < 20; ++slice)	// 2s, pumped + animated
+				{
+					RelayWaitTick("WAITING FOR THE OPERATOR'S SESSION", detail);
+					Sleep(100);
+				}
+			}
 			continue;
 		}
 		Logical got_seat = False;
@@ -1564,6 +1592,8 @@ Logical L4NetworkManager::RelayRequestSeat()
 				tv.tv_usec = 200000;
 				if (select(0, &read_set, NULL, NULL, &tv) != 1)
 				{
+					RelayWaitTick("WAITING FOR THE OPERATOR'S SESSION",
+						"requesting a seat...");
 					continue;
 				}
 				int received = recv(seat_socket, reply + have,