Enable 3D viewer in KiCad WASM build

Build the 3D viewer code for WASM instead of stubbing it out.
This is simpler to maintain than complex header stubs.

Changes:
- Enable KICAD_BUILD_3D_VIEWER_WASM=ON in build script
- Remove -gsource-map to avoid OOM in wasm-emscripten-finalize
- Add OpenGL stubs for fixed-function pipeline (WebGL ES 2.0 only)
- Add GLU stub for gluErrorString
- Add NNG stub for IPC API (sockets don't work in WASM)
- Add PCBnew scripting stub
- Expand curl and libgit2 stubs

The 3D viewer code compiles but won't render at runtime since
OpenGL GAL is disabled and Cairo GAL is used instead.

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

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

wasm/stubs/curl_stub.c

@@ -2,8 +2,68 @@
  * Network operations need to go through JavaScript fetch API
  */
 
+#include <stddef.h>
+#include <stdarg.h>
+
+typedef void CURL;
+typedef void CURLM;
 typedef int CURLcode;
+typedef int CURLoption;
+typedef int CURLINFO;
+
 #define CURLE_OK 0
+#define CURLE_UNSUPPORTED_PROTOCOL 1
+
+/* Version info */
+const char* curl_version(void) {
+    return "stub-wasm/0.0 (no network in browser)";
+}
+
+/* Easy interface */
+CURL* curl_easy_init(void) {
+    return NULL;  /* No curl in WASM */
+}
+
+void curl_easy_cleanup(CURL *curl) {
+    (void)curl;
+}
+
+CURLcode curl_easy_setopt(CURL *curl, CURLoption option, ...) {
+    (void)curl;
+    (void)option;
+    return CURLE_OK;
+}
+
+CURLcode curl_easy_perform(CURL *curl) {
+    (void)curl;
+    return CURLE_UNSUPPORTED_PROTOCOL;
+}
+
+CURLcode curl_easy_getinfo(CURL *curl, CURLINFO info, ...) {
+    (void)curl;
+    (void)info;
+    return CURLE_OK;
+}
+
+const char* curl_easy_strerror(CURLcode code) {
+    (void)code;
+    return "Network operations not available in browser";
+}
+
+void curl_easy_reset(CURL *curl) {
+    (void)curl;
+}
+
+char* curl_easy_escape(CURL *curl, const char *string, int length) {
+    (void)curl;
+    (void)string;
+    (void)length;
+    return NULL;
+}
+
+void curl_free(void *p) {
+    (void)p;
+}
 
 CURLcode curl_global_init(long flags) {
     (void)flags;
@@ -13,3 +73,28 @@ CURLcode curl_global_init(long flags) {
 void curl_global_cleanup(void) {
     /* Nothing to clean up */
 }
+
+/* Multi interface (for async) */
+CURLM* curl_multi_init(void) {
+    return NULL;
+}
+
+void curl_multi_cleanup(CURLM *multi) {
+    (void)multi;
+}
+
+/* Slist */
+struct curl_slist {
+    char *data;
+    struct curl_slist *next;
+};
+
+struct curl_slist* curl_slist_append(struct curl_slist *list, const char *string) {
+    (void)list;
+    (void)string;
+    return NULL;
+}
+
+void curl_slist_free_all(struct curl_slist *list) {
+    (void)list;
+}