Fixed

• test_runner.c shim alignment: all 10 test files now have test_xxx_run() shims
• Makefile test integration: Added test_debug_menu.c, test_crc32.c, test_dec_modes.c to TEST_SRCS (64 test cases were previously not compiling)
• Model loading implementation (SHM format)
  • asset_model_load() using sh_mesh_load() from shachi/assets.h
  • NULL pointer and memory allocation error handling
  • asset_model_free() for proper cleanup
• CRC32 validation
  • d3tui_crc32_file() static function (polynomial 0xEDB88320)
  • d3tui_metadata_validate() now uses CRC32 checksum
• ANSI ED/EL erase functions
• Bell callback implementation
• P0 compliance enforcement
  • Removed invalid CDI file (concatenated files are not valid Dreamcast images)
  • Only valid ISO-9660 artifacts remain in builds/