fix: 防止开始节点重名参数被删除

- 校验开始节点参数名并保留冲突输入

- 在字段归一化前拦截重名并补充回归测试

easyflow-ui-admin/packages/tinyflow-ui/src/components/core/DefinedParameterItem.svelte

@@ -7,6 +7,7 @@
   import {useTinyflowStore} from '#store/stores.svelte';
   import {getCurrentNodeId} from '#components/utils/NodeUtils';
   import {
+    isStartFormFieldKeyAvailable,
     renameStartFieldReferencesInNodes,
     removeStartFormField,
     START_NODE_TYPE,
@@ -47,12 +48,15 @@
         }
         return param.formType ? [param.formType] : [];
     });
+    let parameterNameDraft = $state<string | null>(null);
     let displayParamName = $derived.by(() => {
         if (isSystemStartParam) {
             return '用户问题';
         }
-        return param.name;
+        return parameterNameDraft ?? param.name;
     });
+    let parameterNameError = $state('');
+    let parameterNameErrorId = $derived(`parameter-name-error-${param.id || index}`);
 
     const { updateNodeData } = useSvelteFlow();
 
@@ -146,7 +150,27 @@
     };
 
     const updateName = (event: Event) => {
-        const newValue = (event.target as any).value;
+        const input = event.target as HTMLInputElement;
+        const newValue = input.value;
+        if (isStartNodeInputParam) {
+            const normalizedValue = trimString(newValue);
+            if (!normalizedValue) {
+                parameterNameError = '参数名不能为空';
+                parameterNameDraft = newValue;
+                return;
+            }
+            if (!isStartFormFieldKeyAvailable(
+                node?.current?.data as Record<string, any>,
+                param.name || '',
+                normalizedValue
+            )) {
+                parameterNameError = '参数名已存在';
+                parameterNameDraft = newValue;
+                return;
+            }
+        }
+        parameterNameDraft = null;
+        parameterNameError = '';
         updateParameter('name', newValue);
     };
 
@@ -191,10 +215,17 @@
 </script>
 
 
-<div class="input-item">
+<div class="input-item input-item-name">
     <Input style="width: 100%;" value={displayParamName} placeholder="请输入参数名称"
            disabled={param.nameDisabled === true}
+           aria-invalid={parameterNameError ? 'true' : undefined}
+           aria-describedby={parameterNameError ? parameterNameErrorId : undefined}
            oninput={updateName} />
+    {#if parameterNameError}
+        <div id={parameterNameErrorId} class="input-error" role="alert">
+            {parameterNameError}
+        </div>
+    {/if}
 </div>
 <div class="input-item">
     <Checkbox checked={param.required} disabled={param.requiredDisabled === true} onchange={updateRequired} />
@@ -276,6 +307,22 @@
     align-items: center;
   }
 
+  .input-item-name {
+    flex-direction: column;
+    align-items: stretch;
+    gap: 3px;
+  }
+
+  .input-error {
+    font-size: 12px;
+    line-height: 1.4;
+    color: var(--tf-danger-soft-text);
+  }
+
+  :global(.tf-input[aria-invalid='true']) {
+    border-color: var(--tf-danger-soft-border);
+  }
+
   .input-more-setting {
     display: flex;
     flex-direction: column;