feat: add usage command (#281)

src/cli/commands/registry.ts

@@ -25,9 +25,9 @@ export const commands: Record<string, Command> = {
     },
   },
   "/exit": {
-    desc: "Exit and show session stats",
+    desc: "Exit this session",
     handler: () => {
-      // Handled specially in App.tsx to show stats
+      // Handled specially in App.tsx
       return "Exiting...";
     },
   },
@@ -180,6 +180,13 @@ export const commands: Record<string, Command> = {
       return "Opening memory viewer...";
     },
   },
+  "/usage": {
+    desc: "Show session usage statistics and balance",
+    handler: () => {
+      // Handled specially in App.tsx to display usage stats
+      return "Fetching usage statistics...";
+    },
+  },
 };
 
 /**