feat(desktop): Agent 节点加「自主工具 (ReAct)」开关

前端补上 Phase B 的 UI 接缝：agent 节点 nodeCatalog 增 autonomous checkbox
（默认 false）。勾选 → exportDsl 带 config.autonomous=true → dispatcher
走 ReAct 自主调工具。此前能力在后端但画布点不到。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

sundynix-desktop/frontend/src/studio/nodeCatalog.ts

@@ -58,8 +58,9 @@ export const NODE_KINDS: Record<string, NodeKind> = {
       { key: "model", label: "模型", type: "select", options: ["占位 Pool", "ollama:qwen", "vllm:custom"], required: true },
       { key: "system", label: "系统提示词", type: "textarea", placeholder: "你是…" },
       { key: "temperature", label: "温度", type: "number" },
+      { key: "autonomous", label: "自主工具 (ReAct)", type: "checkbox" },
     ],
-    defaults: { model: "占位 Pool", system: "", temperature: 0.7 },
+    defaults: { model: "占位 Pool", system: "", temperature: 0.7, autonomous: false },
   },
   tool: {
     kind: "tool",