Guard nested m98m99 staging paths

wasm-port/tests/browser/interp_smoke.html

@@ -7838,16 +7838,27 @@
         "X IN O1",
       );
 
+      const m98m99DisableFanucSubsFiles = [
+        "test-fanuc.ini",
+        "test-no-fanuc.ini",
+        "test-fanuc.ngc",
+        "test-rs274ngc.ngc",
+      ];
       const m98m99DisableFanucSubsDir = await writeInterpRegressionFiles(
         interp,
         "m98m99/09-disable-fanuc-subs",
-        [
-          "test-fanuc.ini",
-          "test-no-fanuc.ini",
-          "test-fanuc.ngc",
-          "test-rs274ngc.ngc",
-        ],
+        m98m99DisableFanucSubsFiles,
       );
+      const m98m99NestedStagedNgcFiles = [
+        m98m99NestedSubsPath,
+        m98m99SubFollowsMainPath,
+        ...m98m99DisableFanucSubsFiles
+          .filter((file) => file.endsWith(".ngc"))
+          .map((file) => `${m98m99DisableFanucSubsDir}/${file}`),
+      ].map((path) => path.replace("/work/browser-interp/m98m99/", ""));
+      if (m98m99NestedStagedNgcFiles.join(",") !== m98m99RegressionFiles.slice(9, 13).join(",")) {
+        throw new Error("browser_interp_m98m99_nested_staging_manifest: list drift");
+      }
       for (const disableFanucCase of [
         {
           name: "fanuc_ini",