Fix: segfault in ETCP tests and add wintun.dll to gitignore

- Fix segfault in ETCP tests by initializing uECC RNG in sc_init_local_keys()
- Fix segfault during cleanup by adding reference counting to socket_platform_cleanup()
- Add wintun.dll to .gitignore
- Update AGENTS.md and platform compatibility headers

All 19 tests now pass successfully.

lib/socket_compat.c

@@ -8,20 +8,33 @@
 #ifdef _WIN32
 // ==================== Windows Implementation ====================
 
+static int wsa_init_count = 0;
+
 int socket_platform_init(void) {
-    WSADATA wsaData;
-    int result = WSAStartup(MAKEWORD(2, 2), &wsaData);
-    if (result != 0) {
-        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "WSAStartup failed: %d", result);
-        return -1;
+    if (wsa_init_count == 0) {
+        WSADATA wsaData;
+        int result = WSAStartup(MAKEWORD(2, 2), &wsaData);
+        if (result != 0) {
+            DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "WSAStartup failed: %d", result);
+            return -1;
+        }
+        DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "Winsock 2.2 initialized");
     }
-    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "Winsock 2.2 initialized");
+    wsa_init_count++;
+    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "Winsock init count: %d", wsa_init_count);
     return 0;
 }
 
 void socket_platform_cleanup(void) {
-    WSACleanup();
-    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "Winsock cleanup completed");
+    if (wsa_init_count > 0) {
+        wsa_init_count--;
+        if (wsa_init_count == 0) {
+            WSACleanup();
+            DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "Winsock cleanup completed");
+        } else {
+            DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "Winsock init count after cleanup: %d", wsa_init_count);
+        }
+    }
 }
 
 int socket_set_nonblocking(socket_t sock) {