Audio: ENABLE the engine (relax dead AWE-card gate) + diagnose the real silence (task #50)

User reported never hearing any audio. Root-caused: the KB "Audio: DONE" was wrong.
The OpenAL playback chain IS fully implemented (device/buffers/sources; PlayNote
really calls alSourcePlay), but three gaps kept it silent:

1. GATED OFF (the "no sound" root cause): BTL4Application::MakeAudioRenderer returned
   NULL unless the pod's AWE_FRONT/AWE_REAR AWE32-card env vars were set -- authentic
   1995 pod behavior, dead on modern hardware, so the renderer was NEVER created.
   FIXED: default audio ON (BT_NO_AUDIO=1 restores silence; AWE vars still force-on).
   Verified: the OpenAL device now opens with no env vars ([audio] device OPENED).
2. Soundbank STUB: allPresets[2][100] (btstubs.cpp) is zero-init -> PRESET_isImplemented
   false -> 0 buffers load. Sample data exists (AUDIO1/2.RES: EnginePower/LaserAFire/...)
   but the event->sample map is gone (not in the decomp). STILL OPEN.
3. No triggering: the reconstructed game never creates AudioEntities on events. STILL OPEN.

So the device opens but nothing loads/plays yet -- enabling real sound needs the
soundbank reconstructed + the game triggers wired (a proper audio wave). Added a
BT_AUDIO_LOG trace harness across L4AUDRND/L4AUDRES/L4AUDLVL. KB corrected.

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

engine/MUNGA_L4/L4AUDRES.cpp

@@ -1,3 +1,4 @@
+#include <cstdlib>
 #include "mungal4.h"
 #pragma hdrstop
 
@@ -558,6 +559,7 @@ void
 		alGetError();
 		g_buffers = new ALuint[g_numBuffers];
 		alGenBuffers(g_numBuffers,g_buffers);
+		if (getenv("BT_AUDIO_LOG")) DEBUG_STREAM << "[audio] alGenBuffers count=" << g_numBuffers << "\n" << std::flush;
 		ALenum error;
 		if ((error = alGetError()) != AL_NO_ERROR)
 		{