尽快推进：加强OPFS参数备份目录边界验证

结论：真实浏览器app smoke继续使用LinuxCNC rs274ngc_pre.cc save_parameters() 语义，验证OPFS下备份link失败非致命时主参数仍持久化且目录不被误删；未扩展smoke parser功能。

web/test-browser-wasm-smoke-app-sections.js

@@ -39,6 +39,26 @@ export async function runBrowserAppOpfsSections(context) {
       const updatedParameterFile = new TextDecoder().decode(await appSimulator.fs.opfs.readFile("parameters/rs274ngc.var"));
       expectIncludes(updatedParameterFile, "5161\t2.000000",
         "app frame did not replace LinuxCNC parameter state after second parse");
+      const savedParameterBackup = new TextDecoder().decode(await appSimulator.fs.opfs.readFile("parameters/rs274ngc.var.bak"));
+      expectIncludes(savedParameterBackup, "5161\t1.000000",
+        "app frame did not persist LinuxCNC parameter backup into OPFS");
+      await appSimulator.fs.opfs.removeFile("parameters/rs274ngc.var.bak");
+      const backupDirectory = appSimulator.fs.opfs.resolvePath("parameters/rs274ngc.var.bak");
+      appSimulator.fs.module.FS.mkdir(backupDirectory);
+      await appSimulator.fs.opfs.persistDirectory("parameters/rs274ngc.var.bak");
+      parseAppFrameProgram(appFrame, "G21 G90\nG0 X3\nG28.1\nM30\n");
+      await waitFor(
+        () => appFrame.contentDocument?.querySelector("#axisX")?.value === "3.000",
+        "app frame did not parse third program for backup-directory coverage",
+      );
+      const directoryBackupParameterFile = new TextDecoder().decode(await appSimulator.fs.opfs.readFile("parameters/rs274ngc.var"));
+      expectIncludes(directoryBackupParameterFile, "5161\t3.000000",
+        "app frame did not save LinuxCNC parameter state when backup link failed");
+      await context.expectOpfsDirectoryStat(
+        appSimulator,
+        "parameters/rs274ngc.var.bak",
+        "app frame removed an existing OPFS backup directory after LinuxCNC non-fatal backup failure",
+      );
       // LinuxCNC source basis: rs274ngc_pre.cc save_parameters()
       // renames filename + ".new" over filename after a successful save.
       await context.expectOpfsMissing(
@@ -46,9 +66,6 @@ export async function runBrowserAppOpfsSections(context) {
         "parameters/rs274ngc.var.new",
         "app frame did not clean up LinuxCNC temporary parameter file in OPFS",
       );
-      const savedParameterBackup = new TextDecoder().decode(await appSimulator.fs.opfs.readFile("parameters/rs274ngc.var.bak"));
-      expectIncludes(savedParameterBackup, "5161\t1.000000",
-        "app frame did not persist LinuxCNC parameter backup into OPFS");
     } finally {
       await disposeAppFrame(appFrame);
     }
@@ -59,7 +76,7 @@ export async function runBrowserAppOpfsSections(context) {
       await waitForAppControls(restoredAppFrame, "restored app frame did not load CNC controls");
       await waitFor(() => {
         const restoredInput = restoredAppFrame.contentDocument?.querySelector("#programInput");
-        return restoredInput?.value === "G21 G90\nG0 X2\nG28.1\nM30\n";
+        return restoredInput?.value === "G21 G90\nG0 X3\nG28.1\nM30\n";
       }, "app frame did not restore current program from OPFS after reload");
       await waitForAppAlarm(
         restoredAppFrame,
@@ -69,7 +86,7 @@ export async function runBrowserAppOpfsSections(context) {
       await getAppFrameSimulator(restoredAppFrame, "restored app frame did not create OPFS simulator workspace");
       parseAppFrameProgram(
         restoredAppFrame,
-        "G21 G90\nF100\nO10 if [#5161 EQ 2]\nG1 X12\nO10 endif\nM30\n",
+        "G21 G90\nF100\nO10 if [#5161 EQ 3]\nG1 X13\nO10 endif\nM30\n",
       );
       await waitForAppAlarm(
         restoredAppFrame,
@@ -77,7 +94,7 @@ export async function runBrowserAppOpfsSections(context) {
         "restored app frame did not parse program with reloaded parameter state",
       );
       await waitFor(
-        () => restoredAppFrame.contentDocument?.querySelector("#axisX")?.value === "12.000",
+        () => restoredAppFrame.contentDocument?.querySelector("#axisX")?.value === "13.000",
         "app frame did not reload LinuxCNC parameter state from OPFS after reload",
       );
     } finally {