Permission Denied with Retry

Permission denial 应被表示为普通 tool result，这样 agent 才能解释、进行安全 retry，或请求更新 scope。

{
  "schema_version": "0.2.0",
  "decision_id": "perm_01HZ",
  "invocation_id": "inv_write_secret",
  "behavior": "deny",
  "mode": "default",
  "source": "project_settings",
  "reason": {
    "type": "rule",
    "rule_ref": "rule_deny_secrets_dir",
    "message": "Writes under .secrets are denied by project policy."
  },
  "blocked_path": "/workspace/.secrets/token.txt",
  "decided_at": "2026-05-08T00:00:00Z"
}

{
  "schema_version": "0.2.0",
  "result_id": "result_write_secret",
  "invocation_id": "inv_write_secret",
  "status": "denied",
  "is_error": true,
  "error": {
    "error_class": "permission_denied",
    "recoverability": "change_arguments_or_policy",
    "retry_after": null
  },
  "policy_refs": ["policy:project-file-access"],
  "created_at": "2026-05-08T00:00:01Z"
}