feat: Add memory persistence functions (save/load-memory-to-disk)

- Add save-memory-to-disk and load-memory-from-disk to memory.lisp
- Integrate auto-save into heartbeat (every N intervals)
- Load memory on daemon startup, save on graceful shutdown/SIGINT
- Add exports to package.lisp

NOTE: Hash table serialization requires object walker for complex structures.
      Current implementation fails on load due to unreadable objects.

library/loop.lisp

@@ -39,24 +39,43 @@
                   (setf current-signal (list :type :EVENT :depth (1+ depth) :meta meta
                                              :payload (list :sensor :loop-error :message (format nil "~a" c) :depth depth)))))))))))
 
+(defvar *auto-save-interval* 300
+  "Save memory to disk every N seconds. Set from MEMORY_AUTO_SAVE_INTERVAL env.")
+
+(defvar *heartbeat-save-counter* 0
+  "Counter for auto-save triggers.")
+
 (defun start-heartbeat ()
   "Starts the background heartbeat thread. Interval is loaded from HEARTBEAT_INTERVAL."
-  (let ((interval (or (ignore-errors (parse-integer (uiop:getenv "HEARTBEAT_INTERVAL"))) 60)))
+  (let ((interval (or (ignore-errors (parse-integer (uiop:getenv "HEARTBEAT_INTERVAL"))) 60))
+        (auto-save (or (ignore-errors (parse-integer (uiop:getenv "MEMORY_AUTO_SAVE_INTERVAL"))) *auto-save-interval*)))
+    (setf *auto-save-interval* auto-save)
+    (setf *heartbeat-save-counter* 0)
     (setf *heartbeat-thread* 
           (bt:make-thread 
            (lambda () 
              (loop 
                (sleep interval) 
+               (incf *heartbeat-save-counter*)
+               (when (>= *heartbeat-save-counter* (/ *auto-save-interval* interval))
+                 (setf *heartbeat-save-counter* 0)
+                 (save-memory-to-disk))
                ;; inject-stimulus is synchronous for heartbeats, preventing accumulation.
                (inject-stimulus (list :type :EVENT :payload (list :sensor :heartbeat :unix-time (get-universal-time)))))) 
            :name "opencortex-heartbeat"))))
 
+(defvar *shutdown-save-enabled* t
+  "If non-nil, save memory to disk on graceful shutdown.")
+
 (defun main ()
   "Entry point for the Skeleton MVP. Handles initialization and graceful shutdown."
   (let* ((home (uiop:getenv "HOME"))
          (env-file (uiop:merge-pathnames* ".local/share/opencortex/.env" (uiop:ensure-directory-pathname home))))
     (when (uiop:file-exists-p env-file) (cl-dotenv:load-env env-file)))
-  
+
+  ;; Load memory from disk if a snapshot exists
+  (load-memory-from-disk)
+
   (initialize-actuators)
   (initialize-all-skills)
 
@@ -67,10 +86,14 @@
   (sb-sys:enable-interrupt sb-unix:sigint 
                            (lambda (sig code scp) 
                              (declare (ignore sig code scp)) 
-                             (harness-log "SHUTDOWN: SIGINT received. Exiting...")
+                             (harness-log "SHUTDOWN: SIGINT received. Saving memory...")
+                             (when *shutdown-save-enabled* (save-memory-to-disk))
                              (uiop:quit 0)))
 
   (let ((sleep-interval (or (ignore-errors (parse-integer (uiop:getenv "DAEMON_SLEEP_INTERVAL"))) 3600)))
     (loop 
-      (when (bt:with-lock-held (*interrupt-lock*) *interrupt-flag*) (return))
+      (when (bt:with-lock-held (*interrupt-lock*) *interrupt-flag*)
+        (harness-log "SHUTDOWN: Interrupt flag set. Saving memory...")
+        (when *shutdown-save-enabled* (save-memory-to-disk))
+        (return))
       (sleep sleep-interval))))