fix: 优先审批 + 首用户隔离 + 审批DB闭环 + memo错误

1. (High) 内置工具先审批再执行 — is_builtin 检查优先，
   High 风险通过 builtin_approve 后再调用 BuiltinRegistry
2. (High) 首用户 current_user_id — 移除 !is_empty() 守卫
3. (Medium) 审批 DB 状态闭环 — 取消/错误时按 user_id 更新最近 pending
4. (Medium) manage_memos 写入失败 — .ok() → 完整错误返回

src/tools/approval.rs

@@ -126,12 +126,12 @@ impl ApprovalManager {
                 ApprovalDecision::Approved => "approved",
                 _ => "rejected",
             };
+            // 按 user_id + 最近 pending 记录更新
             let _ = sqlx::query(
-                "UPDATE pending_approvals SET status = $1, consumed_at = NOW() WHERE user_id = $2 AND code_hash = $3 AND status = 'pending'",
+                "UPDATE pending_approvals SET status = $1, consumed_at = NOW() WHERE user_id = $2 AND status = 'pending' ORDER BY created_at DESC LIMIT 1",
             )
             .bind(status)
             .bind(user_id)
-            .bind(&format!("{:x}", Sha256::digest(reply.as_bytes())))
             .execute(pool.as_ref())
             .await;
         }