fix(tcp): MUX模式网口失联 — 对端关闭时用tcp_abort替代tcp_close避免TIME_WAIT耗尽pcb池

根因: tcp_close()将对端关闭的pcb推入TIME_WAIT(120s), 占用MEMP_TCP_PCB池(仅4个),
多连接同时断开后pcb池耗尽, tcp_new()返回NULL, 新连接无法建立直到120s超时释放。

核心修复:
- tcp_server/client: 对端关闭(p=NULL)时tcp_abort替代tcp_close, pcb立即释放
- ch390_runtime: PKT_ERR恢复强制OR上RCR_RXEN(与WCH官方一致)
- ch390_runtime: TX连续超时3次自动emergency reset
- ch390_runtime: 每5秒health_check读VID验证芯片存活
- main: App_StartLinksIfNeeded失败时不标记g_links_started, 允许重试
- main: MUX逐帧RTT printf改为#if DEBUG门控, 减少主循环延迟
- uart_trans: MUX帧解析改为先搜0x7E再消费header, 非法帧只丢1字节

Drivers/CH390/ch390_runtime.h

@@ -58,5 +58,8 @@ void ch390_runtime_check_link(struct netif *netif);
 err_t ch390_runtime_output(struct netif *netif, struct pbuf *p);
 void ch390_runtime_get_diag(ch390_diag_t *diag);
 bool ch390_runtime_is_ready(void);
+bool ch390_runtime_emergency_reset(void);
+void ch390_runtime_health_check(struct netif *netif);
+uint8_t ch390_runtime_get_reset_count(void);
 
 #endif