接续L4-TOOL-DB浏览器Worker边界

结论：浏览器 Tool DB Worker 传输层已接入并明确阻塞缺失的 Python/WASM runtime，未冒充 DB_PROGRAM 执行就绪。

wasm-port/runtime/workers/tool-db-python-worker.js

@@ -0,0 +1,39 @@
+function postReply(id, type, payload) {
+  self.postMessage({ id, type, ok: true, ...payload });
+}
+
+function postError(id, type, error) {
+  self.postMessage({
+    id,
+    type,
+    ok: false,
+    error: error?.message ?? String(error),
+  });
+}
+
+function pythonRuntimeAvailable() {
+  return typeof self.loadPyodide === "function" || Boolean(self.pyodide?.runPythonAsync);
+}
+
+self.addEventListener("message", async (event) => {
+  const message = event.data ?? {};
+  const { id, type } = message;
+  try {
+    if (type === "start") {
+      const ready = pythonRuntimeAvailable();
+      postReply(id, type, {
+        runtimeMode: "browser-python-wasm-worker",
+        runtimeExecutionReady: ready,
+        status: ready
+          ? "browser_python_wasm_runtime_ready"
+          : "blocked_browser_python_wasm_runtime_missing",
+        executionEnabled: false,
+        promotionAllowed: false,
+      });
+      return;
+    }
+    throw new Error("blocked_browser_python_wasm_runtime_missing");
+  } catch (error) {
+    postError(id, type, error);
+  }
+});