Add timeout to OWN_GIL context shutdown

Prevents hanging forever if Python thread is stuck. Uses 30 second
timeout with platform-specific implementation:
- Linux: pthread_timedjoin_np() with deadline
- macOS/other: poll thread_running flag

On timeout, logs warning and detaches thread instead of blocking.

Author: benoitc

c_src/py_nif.c

@@ -4115,8 +4115,12 @@ static int owngil_context_init(py_context_t *ctx) {
 /**
  * @brief Shutdown OWN_GIL context and clean up resources
  *
+ * Uses a timeout to avoid hanging forever if the Python thread is stuck.
+ *
  * @param ctx Context to shutdown
  */
+#define OWNGIL_SHUTDOWN_TIMEOUT_SECS 30
+
 static void owngil_context_shutdown(py_context_t *ctx) {
     if (!ctx->uses_own_gil) {
         return;
@@ -4130,8 +4134,33 @@ static void owngil_context_shutdown(py_context_t *ctx) {
     pthread_cond_signal(&ctx->request_ready);
     pthread_mutex_unlock(&ctx->request_mutex);
 
-    /* Wait for thread to exit */
-    pthread_join(ctx->own_gil_thread, NULL);
+    /* Wait for thread to exit with timeout */
+#if defined(__linux__)
+    struct timespec deadline;
+    clock_gettime(CLOCK_REALTIME, &deadline);
+    deadline.tv_sec += OWNGIL_SHUTDOWN_TIMEOUT_SECS;
+    int rc = pthread_timedjoin_np(ctx->own_gil_thread, NULL, &deadline);
+    if (rc == ETIMEDOUT) {
+        fprintf(stderr, "OWN_GIL shutdown timeout after %d seconds, detaching thread\n",
+                OWNGIL_SHUTDOWN_TIMEOUT_SECS);
+        pthread_detach(ctx->own_gil_thread);
+    }
+#else
+    /* macOS/other: poll thread_running flag with timeout */
+    int wait_ms = 0;
+    while (atomic_load(&ctx->thread_running) &&
+           wait_ms < OWNGIL_SHUTDOWN_TIMEOUT_SECS * 1000) {
+        usleep(100000);  /* 100ms */
+        wait_ms += 100;
+    }
+    if (atomic_load(&ctx->thread_running)) {
+        fprintf(stderr, "OWN_GIL shutdown timeout after %d seconds, detaching thread\n",
+                OWNGIL_SHUTDOWN_TIMEOUT_SECS);
+        pthread_detach(ctx->own_gil_thread);
+    } else {
+        pthread_join(ctx->own_gil_thread, NULL);
+    }
+#endif
 
     /* Clean up resources */
     if (ctx->shared_env != NULL) {