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>

CMakeLists.txt

@@ -281,6 +281,7 @@ add_library(bt410_l4 STATIC
   "game/reconstructed/thermalsight.cpp"
   "game/reconstructed/torso.cpp"
   "game/reconstructed/btstubs.cpp"
+  "game/reconstructed/audiopresets.cpp"
   "game/reconstructed/dpl2d.cpp"
   "game/original/BT/BTMSSN.CPP"
   "game/original/BT/BTREG.CPP"
@@ -319,7 +320,6 @@ target_link_libraries(btl4 PRIVATE
     bt410_l4
     munga_engine
     "${CMAKE_SOURCE_DIR}/engine/lib/OpenAL32.lib"
-    "${CMAKE_SOURCE_DIR}/engine/lib/libsndfile-1.lib"
     "${DXSDK}/Lib/x86/d3d9.lib"
     "${DXSDK}/Lib/x86/d3dx9.lib"
     "${DXSDK}/Lib/x86/dinput8.lib"
@@ -331,9 +331,10 @@ target_link_libraries(btl4 PRIVATE
 # UNRESOLVED tolerates the dead offline-tool factory in mech3.cpp.  See docs.
 target_link_options(btl4 PRIVATE /FORCE)
 
-# Copy the third-party runtime DLLs next to the built exe.
+# Copy the OpenAL runtime DLL next to the built exe.  (libsndfile is gone: its
+# repo DLL was a no-op STUB -- L4AUDRES now loads the soundbank WAVs with an
+# in-tree RIFF/PCM reader, no external dependency.)
 add_custom_command(TARGET btl4 POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E copy_if_different
         "${CMAKE_SOURCE_DIR}/engine/lib/OpenAL32.dll"
-        "${CMAKE_SOURCE_DIR}/engine/lib/libsndfile-1.dll"
         "$<TARGET_FILE_DIR:btl4>")