fix: make autosave_running atomic to fix data race in thread shutdown

Co-authored-by: aider (deepseek/deepseek-coder) <aider@aider.chat>

fs.c

@@ -10,6 +10,7 @@
 #include <sys/types.h>
 #include <dirent.h>
 #include <time.h>
+#include <stdatomic.h>
 
 // ============================================================
 // Auto-save thread
@@ -18,7 +19,7 @@
 static pthread_t autosave_thread;
 static pthread_mutex_t autosave_mutex = PTHREAD_MUTEX_INITIALIZER;
 static pthread_cond_t autosave_cond = PTHREAD_COND_INITIALIZER;
-static volatile bool autosave_running = false;
+static atomic_bool autosave_running = false;
 static volatile bool autosave_pending = false;
 static time_t last_autosave_time = 0;
 
@@ -35,11 +36,11 @@ static void ensure_autosave_dir(void) {
 static void* autosave_thread_func(void *arg) {
     (void)arg;
     
-    while (autosave_running) {
+    while (atomic_load(&autosave_running)) {
         pthread_mutex_lock(&autosave_mutex);
         
         // Wait for trigger or shutdown
-        while (autosave_running && !autosave_pending) {
+        while (atomic_load(&autosave_running) && !autosave_pending) {
             struct timespec ts;
             clock_gettime(CLOCK_REALTIME, &ts);
             ts.tv_sec += 5;  // Wake up every 5 seconds to check
@@ -101,14 +102,14 @@ static void* autosave_thread_func(void *arg) {
 }
 
 void fs_init(void) {
-    autosave_running = true;
+    atomic_store(&autosave_running, true);
     autosave_pending = false;
     ensure_autosave_dir();
     pthread_create(&autosave_thread, NULL, autosave_thread_func, NULL);
 }
 
 void fs_cleanup(void) {
-    autosave_running = false;
+    atomic_store(&autosave_running, false);
     pthread_cond_signal(&autosave_cond);
     pthread_join(autosave_thread, NULL);
 }