按规划继续工作

结论：补齐浏览器 OPFS 参数备份读回验证，继续通过 vendored LinuxCNC save_parameters 备份路径覆盖持久化边界。

wasm-port/tests/browser/interp_smoke.html

@@ -15,6 +15,7 @@
       saveMachineParametersToOpfs,
     } from "../../runtime/opfs/linuxcnc-parameter-bridge.js";
     import {
+      loadTextFile,
       saveTextFile,
     } from "../../runtime/opfs/file-service.js";
     import {
@@ -384,6 +385,23 @@
           "absent=<_named_param>",
         ].join("\n"),
       );
+      if (
+        savedParameters.backupOpfsPath !==
+        "linuxcnc/machines/browser-interp/linuxcnc.var.bak"
+      ) {
+        throw new Error(`unexpected parameter backup path: ${savedParameters.backupOpfsPath}`);
+      }
+      verifyExpectedOutput(
+        "opfs_saved_parameter_backup_text",
+        await loadTextFile(savedParameters.backupOpfsPath),
+        [
+          "5161 10.5",
+          "5162 20.25",
+          "5221 2.25",
+          "5399 44",
+          "<_named_param> 123",
+        ].join("\n"),
+      );
       const savedToolTable = await saveMachineToolTableToOpfs(
         interp,
         "browser-interp",