fix: 节点离线时允许删除隧道关联，但禁止新增隧道 (#342)

- prepareTunnelCreateState: 更新隧道时允许已关联的离线节点，仅拒绝新增的离线节点
- syncForwardServicesWithWarnings: 离线节点跳过下发并返回警告，不再硬性失败
- applyTunnelRuntime: 所有节点类型均支持离线错误延迟处理
- 前端 validateTunnelForm: 编辑模式下跳过离线节点验证

Closes #342

vite-frontend/src/pages/tunnel.tsx

@@ -418,7 +418,7 @@ export default function TunnelPage() {
 
   // 表单验证
   const validateForm = (): boolean => {
-    const newErrors = validateTunnelForm(form, nodes);
+    const newErrors = validateTunnelForm(form, nodes, isEdit);
 
     setErrors(newErrors);
 

vite-frontend/src/pages/tunnel/form.ts

@@ -33,6 +33,7 @@ export const createTunnelFormDefaults = () => {
 export const validateTunnelForm = (
   form: TunnelFormInput,
   nodes: TunnelNodeInput[],
+  isEdit = false,
 ): Record<string, string> => {
   const errors: Record<string, string> = {};
 
@@ -44,7 +45,9 @@ export const validateTunnelForm = (
 
   if (!form.inNodeId || form.inNodeId.length === 0) {
     errors.inNodeId = "请至少选择一个入口节点";
-  } else {
+  } else if (!isEdit) {
+    // Only enforce online check for new tunnels. During edit the backend
+    // allows existing offline nodes (user may be removing them).
     const offlineInNodes = form.inNodeId.filter((item) => {
       const node = nodes.find((n) => n.id === item.nodeId);
 
@@ -64,14 +67,16 @@ export const validateTunnelForm = (
     if (!form.outNodeId || form.outNodeId.length === 0) {
       errors.outNodeId = "请至少选择一个出口节点";
     } else {
-      const offlineOutNodes = form.outNodeId.filter((item) => {
-        const node = nodes.find((n) => n.id === item.nodeId);
+      if (!isEdit) {
+        const offlineOutNodes = form.outNodeId.filter((item) => {
+          const node = nodes.find((n) => n.id === item.nodeId);
 
-        return node && node.status !== 1;
-      });
+          return node && node.status !== 1;
+        });
 
-      if (offlineOutNodes.length > 0) {
-        errors.outNodeId = "所有出口节点必须在线";
+        if (offlineOutNodes.length > 0) {
+          errors.outNodeId = "所有出口节点必须在线";
+        }
       }
 
       const inNodeIds = form.inNodeId.map((item) => item.nodeId);