Update core library to use real wxBase instead of wx_shim

- Update CMakeLists.txt to link against wxBase WASM build
- Move config.h to wasm-config/ to avoid conflicts with wx headers
- Add build-core-wasm.sh script for reproducible builds
- Core now compiles with actual wxString, wxFile, etc. from wxWidgets

Libraries built:
- libkicad_core_utils.a (34K)
- libkimath.a (969K)
- libsexpr.a (45K)
- libclipper2.a (169K)

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

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

core/wasm-config/config.h

@@ -0,0 +1,31 @@
+/*
+ * config.h - Minimal config for kicad-core standalone build
+ *
+ * This replaces the auto-generated config.h from KiCad's CMake
+ */
+
+#ifndef KICAD_CORE_CONFIG_H
+#define KICAD_CORE_CONFIG_H
+
+// Platform detection for timing functions
+#if defined(_WIN32)
+    // Windows uses GetSystemTimeAsFileTime
+#elif defined(__EMSCRIPTEN__) || defined(__APPLE__) || defined(__linux__) || defined(__unix__)
+    #define HAVE_CLOCK_GETTIME 1
+#else
+    #define HAVE_GETTIMEOFDAY_FUNC 1
+#endif
+
+// Version info
+#define KICAD_MAJOR_VERSION 8
+#define KICAD_MINOR_VERSION 0
+#define KICAD_PATCH_VERSION 0
+#define KICAD_VERSION_FULL "8.0.0-wasm"
+
+// Feature flags - all disabled for core-only build
+#define KICAD_USE_CURL 0
+#define KICAD_USE_GIT 0
+#define KICAD_USE_OCC 0
+#define KICAD_USE_NGSPICE 0
+
+#endif // KICAD_CORE_CONFIG_H