feat(security): grow Yerin's toolset (pending_review, resource_exposure, token_audit)

Three more read-only tools on securityRegistry:
- pending_review: agent-proposed changes awaiting approval (injection surface)
- resource_exposure: host/url/status attack-surface inventory (resources.listExposure,
  scalar cols only — no monitoring/metadata/credentials)
- token_audit: token label/last_used/revoked, never the hash

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/ai/agent/tools/security/token_audit.js

@@ -0,0 +1,13 @@
+import * as agents from '../../../../db/repos/agents.js';
+
+// Agent credential hygiene: which tokens exist, when last used, whether revoked.
+// Backed by agents.listTokenMeta — token_hash is never selected.
+export const tokenAuditTool = {
+  name: 'token_audit',
+  description: 'List agent API tokens with label, last_used and revoked status (never the secret) so you can spot stale, unused, or unexpected credentials. Recommend revoking anything dormant.',
+  input_schema: { type: 'object', properties: {} },
+  async handler(_args, _ctx) {
+    const tokens = await agents.listTokenMeta();
+    return { tokens };
+  }
+};