Add Emscripten debug build targets with DWARF and source maps, closes #238

Adds MCRF_WASM_DEBUG CMake option that enables -g4, -gsource-map, and
--emit-symbol-map for WASM builds. New Makefile targets: wasm-debug,
playground-debug, serve-wasm-debug, serve-playground-debug.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CMakeLists.txt

@@ -28,6 +28,7 @@ option(MCRF_SANITIZE_ADDRESS "Build with AddressSanitizer" OFF)
 option(MCRF_SANITIZE_UNDEFINED "Build with UBSan" OFF)
 option(MCRF_SANITIZE_THREAD "Build with ThreadSanitizer" OFF)
 option(MCRF_DEBUG_PYTHON "Link against debug CPython from __lib_debug/" OFF)
+option(MCRF_WASM_DEBUG "Build WASM with DWARF debug info and source maps" OFF)
 
 # Validate mutually exclusive sanitizers
 if(MCRF_SANITIZE_ADDRESS AND MCRF_SANITIZE_THREAD)
@@ -398,6 +399,17 @@ if(EMSCRIPTEN)
         message(STATUS "Emscripten SDL2 options enabled: -sUSE_SDL=2 -sUSE_SDL_MIXER=2 -sFULL_ES2=1 -sUSE_FREETYPE=1")
     endif()
 
+    # WASM debug builds: DWARF symbols, source maps, symbol map for stack traces
+    if(MCRF_WASM_DEBUG)
+        list(APPEND EMSCRIPTEN_LINK_OPTIONS
+            -g4
+            -gsource-map
+            --emit-symbol-map
+        )
+        target_compile_options(mcrogueface PRIVATE -g4)
+        message(STATUS "Emscripten debug enabled: DWARF (-g4), source maps, symbol map")
+    endif()
+
     target_link_options(mcrogueface PRIVATE ${EMSCRIPTEN_LINK_OPTIONS})
 
     # Output as HTML to use the shell file