fix: Fix variable insertion to only trigger on current line

web/app/components/workflow/nodes/tool/components/mixed-variable-text-input/index.tsx

@@ -500,8 +500,13 @@ const MixedVariableTextInput = ({
     if (!onChange)
       return
 
-    // compute words after the latest '@' and delete them
-    const valueWithoutTrigger = value.replace(/@[^@\n]*$/, '')
+    const valueWithoutTrigger = (() => {
+      const lineStart = value.lastIndexOf('\n') + 1
+      const triggerIndex = value.lastIndexOf('@')
+      if (triggerIndex < lineStart)
+        return value
+      return value.slice(0, triggerIndex)
+    })()
     const newValue = `{{@${agent.id}.context@}}${valueWithoutTrigger}`
 
     if (toolNodeId && paramKey) {