Improve build system with debug symbols, clean modes, and parallel jobs

- Add build.md documentation for the WASM build system
- Default to debug builds with -gsource-map for WASM debugging
- Add --release flag to disable debug symbols
- Add --clean flag for full rebuild (deps + wxWidgets + KiCad)
- Add -j N flag for parallel compilation (default: 1 for sequential)
- Update Docker memory limit to 32GB
- Propagate DEBUG_BUILD and JOBS to all dependency scripts

Build modes:
- ./docker/build.sh --clean -j8  (full rebuild, parallel)
- ./docker/build.sh              (rebuild KiCad only)
- ./docker/build.sh --no-clean   (incremental)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

scripts/build-kicad-wasm.sh

@@ -9,7 +9,8 @@
 #   --with-occ      Enable OpenCASCADE (3D/STEP support)
 #   --with-ngspice  Enable ngspice (simulation)
 #   --with-pthread  Enable pthreads (multi-threading)
-#   --debug         Debug build with symbols
+#   --release       Release build (optimized, no debug symbols)
+#   --debug         Debug build with symbols (default)
 #   -j N            Parallel jobs (default: nproc)
 #   --help          Show this help
 
@@ -66,6 +67,10 @@ while [[ $# -gt 0 ]]; do
             DEBUG_BUILD=1
             shift
             ;;
+        --release)
+            DEBUG_BUILD=0
+            shift
+            ;;
         -j)
             PARALLEL_JOBS="$2"
             shift 2
@@ -83,7 +88,7 @@ done
 
 # Set defaults if not set
 CLEAN_BUILD=${CLEAN_BUILD:-0}
-DEBUG_BUILD=${DEBUG_BUILD:-0}
+DEBUG_BUILD=${DEBUG_BUILD:-1}  # Debug mode by default (use --release for optimized builds)
 PARALLEL_JOBS=${PARALLEL_JOBS:-$(get_nproc)}
 
 # Export for sub-scripts