feat(cli): implement sessions list command

src/cli/sessions.ts

@@ -1,12 +1,50 @@
 import type { Command } from 'commander';
+import type { SessionStore } from '../session/index.js';
+import { getDataDir } from './shared.js';
+import { resolve } from 'path';
+
+export interface SessionInfo {
+  id: string;
+  messageCount: number;
+}
+
+/** List all sessions with their message counts. */
+export function listSessions(store: SessionStore): SessionInfo[] {
+  const sessionIds = store.listSessions();
+  return sessionIds.map((id) => ({
+    id,
+    messageCount: store.getMessages(id).length,
+  }));
+}
 
 export function registerSessionsCommand(program: Command): void {
   program
     .command('sessions')
     .description('List active sessions')
-    .option('-c, --config <path>', 'Config file path')
-    .action(async (_opts: { config?: string }) => {
-      console.error('Not yet implemented');
-      process.exit(1);
+    .action(async () => {
+      const dataDir = getDataDir();
+      const dbPath = resolve(dataDir, 'sessions.db');
+
+      const { SessionStore: Store } = await import('../session/index.js');
+      const store = new Store(dbPath);
+
+      try {
+        const sessions = listSessions(store);
+
+        if (sessions.length === 0) {
+          console.log('No sessions found.');
+          return;
+        }
+
+        console.log('Sessions:');
+        console.log('');
+        for (const session of sessions) {
+          console.log(`  ${session.id}  (${session.messageCount} messages)`);
+        }
+        console.log('');
+        console.log(`Total: ${sessions.length} session(s)`);
+      } finally {
+        store.close();
+      }
     });
 }