feat: add AssembleVariablesAlt icon and integrate into sub-graph

components.

web/app/components/workflow/nodes/sub-graph-start/constants.ts

@@ -0,0 +1 @@
+export const CUSTOM_SUB_GRAPH_START_NODE = 'custom-sub-graph-start'

web/app/components/workflow/nodes/sub-graph-start/index.tsx

@@ -0,0 +1,60 @@
+import type { NodeProps } from 'reactflow'
+import type { CommonNodeType } from '@/app/components/workflow/types'
+import { memo } from 'react'
+import { useTranslation } from 'react-i18next'
+import { AssembleVariablesAlt } from '@/app/components/base/icons/src/vender/line/general'
+import { Agent } from '@/app/components/base/icons/src/vender/workflow'
+import Tooltip from '@/app/components/base/tooltip'
+import { NodeSourceHandle } from '@/app/components/workflow/nodes/_base/components/node-handle'
+import { cn } from '@/utils/classnames'
+
+type SubGraphStartNodeData = CommonNodeType<{
+  tooltip?: string
+  iconType?: string
+}>
+
+type IconComponent = typeof Agent
+
+const iconMap: Record<string, IconComponent> = {
+  agent: Agent,
+  assemble: AssembleVariablesAlt,
+}
+
+const SubGraphStartNode = ({ id, data }: NodeProps<SubGraphStartNodeData>) => {
+  const { t } = useTranslation()
+  const iconType = data?.iconType || 'agent'
+  const Icon = iconMap[iconType] || Agent
+  const rawTitle = data?.title?.trim() || ''
+  const showTitle = iconType === 'agent' && !!rawTitle
+  const displayTitle = showTitle && (rawTitle.startsWith('@') ? rawTitle : `@${rawTitle}`)
+  const tooltip = data?.tooltip
+    || (iconType === 'assemble' ? t('blocks.start', { ns: 'workflow' }) : (data?.title || t('blocks.start', { ns: 'workflow' })))
+
+  return (
+    <div
+      className={cn(
+        'nodrag group mt-1 flex h-11 items-center justify-center rounded-2xl border border-workflow-block-border bg-workflow-block-bg shadow-xs',
+        showTitle ? 'gap-1.5 px-2' : 'w-11',
+      )}
+    >
+      <Tooltip popupContent={tooltip} asChild={false}>
+        <div className="flex h-6 w-6 items-center justify-center rounded-full border-[0.5px] border-components-panel-border-subtle bg-util-colors-blue-brand-blue-brand-500">
+          <Icon className="h-3 w-3 text-text-primary-on-surface" />
+        </div>
+      </Tooltip>
+      {showTitle && (
+        <span className="system-xs-medium max-w-[160px] truncate text-text-secondary">
+          {displayTitle}
+        </span>
+      )}
+      <NodeSourceHandle
+        id={id}
+        data={data}
+        handleClassName="!top-1/2 !-right-[9px] !-translate-y-1/2"
+        handleId="source"
+      />
+    </div>
+  )
+}
+
+export default memo(SubGraphStartNode)