Audio: ENABLE sound -- real OpenAL + in-tree WAV loader; both backend DLLs were no-op STUBS (task #50)

Root cause of "no sound, ever": the two audio backend DLLs shipped in the repo
are fakes. libsndfile-1.dll exports 15 funcs BY ORDINAL ONLY (no names) and
sf_open() always returns NULL; OpenAL32.dll (72KB) imports only KERNEL32 -- no
dsound/wasapi/winmm -- so it is a pure no-op that returns fake handles
(ctx=0x00000001, alGenSources->0) and never touches the hardware. The whole
render->device->buffer->source->play chain ran clean and silent.

Fixes:
- OpenAL32.dll: replace the stub with the real OpenAL Soft 1.25.2 Win32 build
  (imports AVRT/ole32/WINMM, real WASAPI backend). The exe imports the 25 AL
  funcs by NAME so it is a drop-in; alGenSources now yields a live source and
  alSourcePlay reaches AL_PLAYING.
- libsndfile: DROPPED entirely. It is replaced by LoadWavPCM() in L4AUDRES --
  a tiny RIFF/WAVE fmt+data reader that loads our soundbank WAVs (16-bit PCM)
  straight into the AL buffer. Removed the .lib/.dll from the link + copy and
  git-rm'd the stub. (This also kills the "ordinal 50 could not be located in
  libsndfile-1.dll" load-failure popup: adding an sf_strerror import bound to
  an ordinal the 2..16-only stub could not satisfy.)
- Soundbank: 241 samples cracked from AUDIO1/2.RES (SF2 v1.0) by
  tools/sf2extract.py into content/AUDIO/*.wav + the allPresets[2][128] table
  (audiopresets.cpp), replacing the zero-init btstubs stub. All 241 now load
  (alErr=0). BT_AUDIO_TEST plays buffer0 as proof-of-life; BT_AUDIO_LOG traces
  the chain.

Remaining: in-game triggering (AudioEntities on fire/step/engine/explosion)
so PlayNote fires during play -- next audio wave.

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>")