接续L4-TOOL-DB浏览器Provider协议

结论：浏览器 Worker 已支持可插拔 Python runtime provider 的 line I/O，缺真实 Python/WASM runtime 时仍保持阻塞不解锁。

wasm-port/tests/browser/tool_db_fake_python_runtime_worker.js

@@ -0,0 +1,22 @@
+self.linuxCncToolDbPythonRuntimeProvider = {
+  lines: [
+    "v2.1",
+    "T10 P110 D0.10 Z0.10",
+    "FINI (get_cmd)",
+    "FINI (update recvd) t11 p111 d0.33 z0.11",
+    "FINI (update recvd) t14 p0",
+    "FINI (update recvd) t0 p0",
+  ],
+
+  async start() {},
+
+  async writeLine() {},
+
+  async readLine() {
+    return this.lines.shift();
+  },
+
+  async close() {},
+};
+
+await import("../../runtime/workers/tool-db-python-worker.js");

wasm-port/tests/browser/tool_db_process_browser_smoke.html

@@ -85,6 +85,23 @@
       assertEqual(workerPlanResult.promotionAllowed, false, "worker promotion guard");
       await workerPort.close();
 
+      const fakeRuntimeAdapter = createLinuxCncToolDbBrowserWorkerAdapter({
+        workerUrl: new URL("./tool_db_fake_python_runtime_worker.js", import.meta.url),
+      });
+      const fakeRuntimePort = createLinuxCncToolDbProcessPort({
+        dbProgramPath: "./db_nonran.py",
+        runtimeMode: fakeRuntimeAdapter.runtimeMode,
+        runtimeAdapter: fakeRuntimeAdapter,
+      });
+      const fakeRuntimeStart = await fakeRuntimePort.start();
+      assertEqual(fakeRuntimeStart.runtimeExecutionReady, true, "fake provider runtime readiness");
+      assertEqual(fakeRuntimeStart.status, "browser_python_wasm_runtime_ready", "fake provider runtime status");
+      const fakeRuntimePlan = await fakeRuntimePort.runTransactionPlan();
+      assertEqual(fakeRuntimePlan.status, "runtime_adapter_transaction_plan_executed", "fake provider plan");
+      assertEqual(fakeRuntimePlan.promotionAllowed, false, "fake provider promotion guard");
+      assertEqual(validateToolDbTranscript(fakeRuntimePort.exportTranscript()).ready, true, "fake provider transcript");
+      await fakeRuntimePort.close();
+
       const transcript = [
         { direction: "read", line: "v2.1" },
         { direction: "write", line: "g" },