Fix migration to handle locked directories gracefully

src/core/db.ts

@@ -192,6 +192,7 @@ export function getDbForGraph(graphName: string): Database.Database {
  * Migrate existing .memory directory to new graphs system
  */
 export function migrateOldDatabase(): boolean {
+  try {
     const oldDir = path.join(process.cwd(), '.memory');
     const oldDbPath = path.join(oldDir, 'cortex.db');
 
@@ -212,12 +213,22 @@ export function migrateOldDatabase(): boolean {
     // Copy old database to new location
     fs.copyFileSync(oldDbPath, defaultDbPath);
 
-  // Rename old directory as backup
+    // Try to rename old directory as backup (may fail if locked)
+    try {
       const backupDir = `${oldDir}.migrated-${Date.now()}`;
       fs.renameSync(oldDir, backupDir);
-
       console.log(`Migrated .memory database to new multi-graph system`);
       console.log(`Old database backed up to ${backupDir}`);
+    } catch {
+      // Directory might be locked, just leave it
+      console.log(`Migrated .memory database to new multi-graph system`);
+      console.log(`Note: Old .memory directory is in use and was not renamed`);
+    }
 
     return true;
+  } catch {
+    // Migration failed, probably permissions or file lock
+    // Silently continue - the old database will still work
+    return false;
+  }
 }