fix: WAV dump header corruption and early exit handling

- wav_dump_backend: Fix data_size double-counting channels (line 126)
- test_wav_dump: Assert on data_size validation instead of warning
- main: Add SIGINT/SIGTERM handlers to finalize WAV on Ctrl+C
- Guard signal handler code with DEMO_HEADLESS ifdef

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

3 files changed, 30 insertions, 7 deletions

diff --git a/src/audio/backend/wav_dump_backend.cc b/src/audio/backend/wav_dump_backend.cc
index 3f72c87..7427fa9 100644
--- a/src/audio/backend/wav_dump_backend.cc
+++ b/src/audio/backend/wav_dump_backend.cc
@@ -123,7 +123,7 @@ void WavDumpBackend::write_wav_header(FILE* file, uint32_t num_samples) {
   const uint32_t bits_per_sample = 16;
   const uint32_t byte_rate = sample_rate * num_channels * bits_per_sample / 8;
   const uint16_t block_align = num_channels * bits_per_sample / 8;
-  const uint32_t data_size = num_samples * num_channels * bits_per_sample / 8;
+  const uint32_t data_size = num_samples * bits_per_sample / 8;
 
   // RIFF header
   fwrite("RIFF", 1, 4, file);
diff --git a/src/main.cc b/src/main.cc
index 41c881b..45a642a 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -13,6 +13,9 @@
 #include "audio/backend/wav_dump_backend.h"
 #include "util/file_watcher.h"
 #include <vector>
+#if defined(DEMO_HEADLESS)
+#include <csignal>
+#endif
 #endif
 #include "generated/assets.h" // Include generated asset header
 #include "gpu/demo_effects.h" // For GetDemoDuration()
@@ -24,6 +27,17 @@
 #include <cstdlib>
 #include <cstring>
 
+#if !defined(STRIP_ALL) && defined(DEMO_HEADLESS)
+static WavDumpBackend* g_wav_backend_ptr = nullptr;
+static void signal_handler(int sig) {
+  if (g_wav_backend_ptr != nullptr) {
+    g_wav_backend_ptr->shutdown();
+    g_wav_backend_ptr = nullptr;
+  }
+  exit(sig);
+}
+#endif
+
 int main(int argc, char** argv) {
   PlatformState platform_state;
   bool fullscreen_enabled = false;
@@ -93,6 +107,11 @@ int main(int argc, char** argv) {
   if (dump_wav) {
     wav_backend.set_output_file(wav_output_file);
     audio_set_backend(&wav_backend);
+#if defined(DEMO_HEADLESS)
+    g_wav_backend_ptr = &wav_backend;
+    signal(SIGINT, signal_handler);
+    signal(SIGTERM, signal_handler);
+#endif
     printf("WAV dump mode enabled: %s\n", wav_output_file);
   }
 #endif
@@ -262,6 +281,9 @@ int main(int argc, char** argv) {
     printf("\nWAV dump complete: %.2fs physical, %.2fs music time\n",
            physical_time, g_music_time);
 
+#if defined(DEMO_HEADLESS)
+    g_wav_backend_ptr = nullptr;
+#endif
     audio_shutdown();
     gpu_shutdown();
     platform_shutdown(&platform_state);
@@ -269,6 +291,7 @@ int main(int argc, char** argv) {
   }
 #endif
 
+#if !defined(DEMO_HEADLESS)
   int last_width = platform_state.width;
   int last_height = platform_state.height;
 
@@ -360,8 +383,12 @@ int main(int argc, char** argv) {
     audio_update();
   }
 
+#if !defined(STRIP_ALL) && defined(DEMO_HEADLESS)
+  g_wav_backend_ptr = nullptr;
+#endif
   audio_shutdown();
   gpu_shutdown();
   platform_shutdown(&platform_state);
+#endif /* !defined(DEMO_HEADLESS) */
   return 0;
 }
\ No newline at end of file
diff --git a/src/tests/audio/test_wav_dump.cc b/src/tests/audio/test_wav_dump.cc
index eb14652..85b168d 100644
--- a/src/tests/audio/test_wav_dump.cc
+++ b/src/tests/audio/test_wav_dump.cc
@@ -134,12 +134,8 @@ void test_wav_format_matches_live_audio() {
   const uint32_t expected_min_size = expected_bytes_per_sec * 1.5;
   const uint32_t expected_max_size = expected_bytes_per_sec * 2.5;
 
-  // For now, accept if stereo format is correct (main regression test goal)
-  if (header.data_size < expected_min_size ||
-      header.data_size > expected_max_size) {
-    printf("    WARNING: Data size outside expected range\n");
-    // Don't fail on this for now - stereo format is the critical check
-  }
+  assert(header.data_size >= expected_min_size);
+  assert(header.data_size <= expected_max_size);
 
   // Verify file contains actual audio data (not all zeros)
   fseek(f, sizeof(WavHeader), SEEK_SET);