Audio: restore the dropped ExecuteWatchers poll -- polled audio watchers were ALL dead (task #50)

User: "when I start moving all the sounds fade away, no footsteps."  Diagnosis
chain (all empirical, BT_AUDIO_SPATIAL/BT_ATTRBIND_LOG traces):
- The audio head DOES track the mech (listener-relative positioning verified
  while driving) -- not a spatial bug.
- The idle sounds correctly STOP on leaving the standing state; the MOVING
  sounds never started because every POLLED audio watcher was dead:
  the reconstructed Mech::PerformAndWatch replaced the engine performance but
  dropped the ExecuteWatchers() step from the engine tail (Simulation::
  PerformAndWatch = Perform -> ExecuteWatchers -> WriteSimulationUpdate).
  Only PUSHED StateIndicator watchers (SetState->Execute) ever fired -- which
  is exactly why state sounds worked but footsteps/motion-scaled audio didn't.
  FIX: poll ExecuteWatchers() (AreWatchersDelayed-gated) before the update
  write.  Immediately unlocks the polled family: MissileLoaded01/LaserLoaded01
  ready dings, ProgramButton01, motion scales (PlayNote 15 -> 30 per run).

- FootStep (0x1e) backed REAL: was the inert attrPad (an AudioLogicalTrigger
  polls it -- threshold-crossing pulse per foot plant).  New footStep member,
  pulsed by SetBodyAnimation on entering any locomotion clip 1..0x17 (runtime
  stride alternation MEASURED as body states 12<->13 -- the enum-name numbering
  does not match runtime clip ids), decayed by IntegrateMotion (~1/3 s).
- Footstep volume is speed-scaled (AudioMotionScale on LocalVelocity): at
  standstill the transient start computes volume 0 and the renderer drops it
  (LowAudioVolumeThreshold) -- so footfalls are audible at real walking speed.

Diagnostics kept (BT_AUDIO_SPATIAL): spatial dist/vol per source, CLIPPED/DROP/
START at the request gate, vol=0 factor breakdown, scale->0 sends, trigger
notifications, watcher poll-rate probe.

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

game/reconstructed/mech2.cpp

@@ -249,6 +249,22 @@ void
 		animationState.SetState(state);
 		replicantAnimationState.SetState(state);
 	}
+
+	// FootStep pulse: every locomotion-clip transition is one foot plant (the
+	// stride R<->L alternation -- MEASURED at runtime: forward walking alternates
+	// body states 12<->13, so the enum-name numbering above does NOT match the
+	// runtime clip ids; key on the locomotion RANGE instead).  Clips 1..0x17 are
+	// the gait cycle (stand-to-walk through gimp); 0 = standing, >= 0x18 = falls/
+	// knockdown/death (those get collision/fall audio, not a step).  Raise the
+	// Logical the FootStep AudioLogicalTrigger polls; IntegrateMotion decays it
+	// back to 0 a few frames later so each step is a clean rising edge.  [T2]
+	if (state >= 1 && state <= 0x17)
+	{
+		footStep      = 1;
+		footStepDecay = 20;				// ~1/3s: outlives the watcher poll cadence (still < stride period)
+		if (getenv("BT_AUDIO_LOG")) { static int s_fs=0; if (s_fs++<40)
+			DEBUG_STREAM << "[audio] footstep pulse (clip " << state << ") addr=" << (void*)&footStep << "\n" << std::flush; }
+	}
 }
 
 //