Guard SDK sim-config staging paths

wasm-port/tests/browser/interp_smoke.html

@@ -4511,18 +4511,49 @@
       generatedToolTablePath(toolTable.wasmPath, expectedWasmPath);
     }
 
+    function assertSimConfigStagingPlan(machineRel, plan, expectedWasmDir) {
+      if (plan.wasmDir !== expectedWasmDir) {
+        throw new Error(`${machineRel}: browser sim staging root drift`);
+      }
+      if (!plan.iniPath.startsWith(`${expectedWasmDir}/`)) {
+        throw new Error(`${machineRel}: browser sim INI staging path drift`);
+      }
+      if (plan.programPath !== null && !plan.programPath.startsWith(`${expectedWasmDir}/`)) {
+        throw new Error(`${machineRel}: browser sim program staging path drift`);
+      }
+
+      const paths = [];
+      for (const file of plan.files) {
+        if (file.path !== file.wasmPath) {
+          throw new Error(`${file.sourceRel}: browser sim path/wasmPath drift`);
+        }
+        if (!file.wasmPath.startsWith(`${expectedWasmDir}/`)) {
+          throw new Error(`${file.sourceRel}: browser sim file staging root drift`);
+        }
+        if (!file.sourceRel.startsWith("configs/sim/")) {
+          throw new Error(`${file.sourceRel}: browser sim source root drift`);
+        }
+        if (paths.includes(file.wasmPath)) {
+          throw new Error(`${machineRel}: duplicate browser sim staging path ${file.wasmPath}`);
+        }
+        paths.push(file.wasmPath);
+      }
+    }
+
     async function loadSimMachineFiles(machineRel, iniFile, programFile = null) {
       const iniText = await fetchText(
         `../../vendor/linuxcnc/configs/sim/${machineRel}/${iniFile}`,
       );
+      const expectedWasmDir = `/work/browser-sim/${machineRel}`;
       const plan = planSimConfigStaging({
         manifestText: await fetchText("../../tools/source-manifest.txt"),
         machineRel,
         iniFile,
         iniText,
         programFile,
-        wasmDir: `/work/browser-sim/${machineRel}`,
+        wasmDir: expectedWasmDir,
       });
+      assertSimConfigStagingPlan(machineRel, plan, expectedWasmDir);
 
       return {
         ...plan,