Audio: footstep pulse VERIFIED end-to-end to the matcher; volume chain traced (task #50)

Footstep chain progress (each step empirically verified):
- The FootStep watcher is an AudioMatchOf<Logical> (AudioLogicalTrigger extends
  AudioMatchOf, NOT AudioTriggerOf): authored config match=1 -> Start(2.0) on a
  DirectPatchSource.  [trigcfg]/[matchcfg] ctor dumps added.
- The pulse was pinned at 1: the decay lived in IntegrateMotion, which the
  current gait path NEVER CALLS.  Moved to Mech::PerformAndWatch (provably
  per-frame) with a time-based 150ms window sized to the ~10Hz watcher poll.
  The matcher now fires per stride (14/run, was 1).
- Every footstep Start is DROPPED at the renderer: the source's volumeScale is
  0 (five VolumeAudioHandler sends of exactly 0 = inert/one-shot primes).  The
  volume arrives through the authored control chain (AudioControlMultiplier
  inputs ctl 100+; one 0 input pins the product).  Chain scales identified on
  this entity: LocalVelocity (live), LocalAcceleration (live), Myomers.
  SpeedEffect (=1.0 healthy; one authored scale maps [0,1]->[1,0] INVERTED),
  UnstablePercentage (INERT PAD -- always 0!), HeatSink.CurrentTemperature.
  PRIME SUSPECT: an UnstablePercentage-fed multiplier input primes 0 once and
  never updates (the pad never changes), pinning footstep volume at 0.
- SF2 numbering fact recorded: 38 presets in AUDIO1 / 5 in AUDIO2 have
  wPreset != file index (gap at preset 77); my table keys by wPreset.  The
  184x ProgramButton01 (bank1 patch83) storm at ~7/s needs an identity check
  against index-numbering (it may be the wrong sample for that patch id).

Diagnostics added (BT_AUDIO_SPATIAL/BT_ATTRBIND_LOG): [trigcfg]/[matchcfg]
ctor dumps, [matchfire] with component ptr+class, [volset] VolumeAudioHandler,
[mult0] multiplier zero-products, scale sends with authored boundaries,
[fswatch] dedicated footstep watcher tracer (g_btFootStepAddr), SetupPatch
ENTRY with bank/patch/state, Simulation::DebugAudioWatcherCount.

NEXT: back UnstablePercentage with a real (live) member -- it is the mech's
stability 0..1 (the stabilityAlarm/gyro family) -- or confirm via a one-run
chain dump which multiplier input pins the FS source; then the footstep
transient should clear the 0.3 drop gate at walking speed.

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

engine/MUNGA/AUDCMP.cpp

@@ -1,3 +1,4 @@
+#include <cstdlib>
 #include "munga.h"
 #pragma hdrstop
 
@@ -793,6 +794,9 @@ void
       }
 
 		Check(audioComponentSocket.GetCurrent());
+		if (getenv("BT_AUDIO_SPATIAL") && mult_value <= 0.0f) { static int s_mx=0; if (s_mx++<300)
+			DEBUG_STREAM << "[mult0] mult=" << (void*)this << " -> tgt=" << (void*)audioComponentSocket.GetCurrent()
+				<< " in[" << index << "]=" << control_value << " product=" << mult_value << "\n" << std::flush; }
       audioComponentSocket.GetCurrent()->ReceiveControl(
       	outputControlID,
          mult_value