port(audio): D207 diag probe — GE_FORCEALARM

Temporary env-gated probe in handle_alarm_gas_timer_calldamage to force
and trace the alarm klaxon while investigating D207 (user report: alarm
SFX overrides other audio). #ifdef PORT + getenv, inert unless set.
Remove once D207 is resolved (see findings.md D207 / HANDOFF).

src/game/propobj.c

@@ -14450,6 +14450,25 @@ Gfx *countdownTimerRender(Gfx *DL)
 
 void handle_alarm_gas_timer_calldamage(void)
 {
+#ifdef PORT
+    /* D207 diag probe (temporary): force + trace the alarm klaxon to
+     * root-cause "alarm SFX starves all other audio and never recovers".
+     * GE_FORCEALARM pins alarm_timer so alarmIsActive() stays true. Remove
+     * once root-caused. */
+    if (getenv("GE_FORCEALARM")) {
+        static int fa_frames;
+        ++fa_frames;
+        if (fa_frames == 120 || fa_frames == 900) alarmActivate();
+        if (fa_frames > 120 && fa_frames < 600) alarm_timer = 1;  /* sustain on ~2..10s */
+        if (fa_frames == 600) alarmDeactivate();                  /* explicit off at 10s */
+        if (fa_frames > 900) alarm_timer = 1;                     /* sustain on again */
+        geTracePrintf("audiotrace.log",
+            "[D207] f=%d active=%d ptr_alarm_sfx=%p playstate=%d locked=%d\n",
+            fa_frames, (int)alarmIsActive(), (void *)ptr_alarm_sfx,
+            ptr_alarm_sfx ? (int)sndGetPlayingState(ptr_alarm_sfx) : -1,
+            (int)lvlGetControlsLockedFlag());
+    }
+#endif
     if (alarmIsActive() != 0)
     {
         if ((ptr_alarm_sfx == 0) && (lvlGetControlsLockedFlag() == 0))