feat(agent): 聊天提交统一走 POST /agent/runs 异步网关

引入 Agent Run 网关替代直连 /sessions/:id/reply，并在 api_lockdown 白名单中放行新入口，避免策略拦截导致聊天不可用。

Co-authored-by: Cursor <cursoragent@cursor.com>

schema.sql

@@ -353,6 +353,36 @@ CREATE TABLE IF NOT EXISTS h5_user_sessions (
   CONSTRAINT fk_h5_session_user FOREIGN KEY (user_id) REFERENCES h5_users(id) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
 
+CREATE TABLE IF NOT EXISTS h5_agent_runs (
+  id CHAR(36) PRIMARY KEY,
+  user_id CHAR(36) NOT NULL,
+  agent_session_id VARCHAR(128) NULL,
+  request_id VARCHAR(128) NOT NULL,
+  status ENUM('queued', 'running', 'retryable', 'succeeded', 'failed') NOT NULL DEFAULT 'queued',
+  attempts INT NOT NULL DEFAULT 0,
+  user_message_json LONGTEXT NOT NULL,
+  error_message TEXT NULL,
+  created_at BIGINT NOT NULL,
+  updated_at BIGINT NOT NULL,
+  started_at BIGINT NULL,
+  completed_at BIGINT NULL,
+  UNIQUE KEY uq_h5_agent_run_request (user_id, request_id),
+  KEY idx_h5_agent_run_user_status (user_id, status, updated_at),
+  KEY idx_h5_agent_run_session (agent_session_id, updated_at),
+  CONSTRAINT fk_h5_agent_run_user FOREIGN KEY (user_id) REFERENCES h5_users(id) ON DELETE CASCADE,
+  CONSTRAINT fk_h5_agent_run_session FOREIGN KEY (agent_session_id) REFERENCES h5_user_sessions(agent_session_id) ON DELETE SET NULL
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+CREATE TABLE IF NOT EXISTS h5_agent_run_events (
+  id CHAR(36) PRIMARY KEY,
+  run_id CHAR(36) NOT NULL,
+  event_type VARCHAR(64) NOT NULL,
+  data_json JSON NULL,
+  created_at BIGINT NOT NULL,
+  KEY idx_h5_agent_run_event_run (run_id, created_at),
+  CONSTRAINT fk_h5_agent_run_event_run FOREIGN KEY (run_id) REFERENCES h5_agent_runs(id) ON DELETE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
 CREATE TABLE IF NOT EXISTS h5_session_billing_state (
   agent_session_id VARCHAR(128) NOT NULL PRIMARY KEY,
   user_id CHAR(36) NOT NULL,