fix: 已有蓝图时禁用「初始化蓝图」按钮

避免用户误用初始化覆盖已有蓝图，引导使用「更新蓝图描绘」。
disabled 状态加 tooltip 提示原因。

src/components/dashboard/BlueprintModal.tsx

@@ -1141,8 +1141,12 @@ function GovernancePanel({
         <div className="flex gap-2">
           <button
             onClick={() => handleOpenPrompt("init")}
+            disabled={bpStatus?.status !== "none"}
+            title={bpStatus?.status !== "none" ? "该项目已有蓝图，请使用「更新蓝图描绘」" : undefined}
             className={`flex-1 py-1.5 rounded-lg text-xs transition-colors ${
-              promptMode === "init"
+              bpStatus?.status !== "none"
+                ? "border border-gray-100 text-gray-300 cursor-not-allowed"
+                : promptMode === "init"
                 ? "bg-blue-600 text-white"
                 : "border border-gray-200 text-gray-600 hover:bg-gray-50"
             }`}