fix(samples): backend-nodejs-wasm-multithread — migrate to new target API

Same surgical migration as matrix-mt + the await pattern. This sample
was untouched by Group 3 because it's a CLI sample, not browser; only
surfaced when running it on the command line.

- cppjs.config.mjs: build.usePthread → target.runtime: 'mt'
- package.json script: -p WebAssembly →
    -p wasm -a wasm32 -r mt -e node -b release
  (mirrors the st sibling's flags but with -r mt)
- src/index.mjs:
    - Update the dist import path to the target-system naming
      (cppjs-sample-backend-nodejs-wasm-multithread-wasm-wasm32-mt-release.node.js).
    - await Native.sample()/runOnThread()/getThreadResult() — comlink
      proxies the worker calls.
    - Move getThreadResult() into setTimeout's async callback so the
      thread has time to finish.

Verified: `node src/index.mjs` prints both the standard result and
the thread-computed result.

Author: erenkucuker

cppjs-samples/cppjs-sample-backend-nodejs-wasm-multithread/cppjs.config.mjs

@@ -12,7 +12,7 @@ export default {
         base: '../..', /* Delete this line for create-cpp.js */
         output: 'dist',
     },
-    build: {
-        usePthread: true
+    target: {
+        runtime: 'mt',
     }
 };

cppjs-samples/cppjs-sample-backend-nodejs-wasm-multithread/package.json

@@ -6,7 +6,7 @@
   "repository": "https://github.com/bugra9/cpp.js.git",
   "license": "MIT",
   "scripts": {
-    "build": "cppjs build -p WebAssembly"
+    "build": "cppjs build -p wasm -a wasm32 -r mt -e node -b release"
   },
   "dependencies": {
     "cpp.js": "workspace:^",

cppjs-samples/cppjs-sample-backend-nodejs-wasm-multithread/src/index.mjs

@@ -1,9 +1,9 @@
-import initCppJs from '../dist/cppjs-sample-backend-nodejs-wasm.node.js';
+import initCppJs from '../dist/cppjs-sample-backend-nodejs-wasm-multithread-wasm-wasm32-mt-release.node.js';
 
-initCppJs().then(({ Native }) => {
-    console.log(`Matrix multiplier with c++ => ${Native.sample()}`);
-    Native.runOnThread();
-    setTimeout(() => {
-        console.log(`Thread result: ${Native.getThreadResult()}`);
+initCppJs().then(async ({ Native }) => {
+    console.log(`Matrix multiplier with c++ => ${await Native.sample()}`);
+    await Native.runOnThread();
+    setTimeout(async () => {
+        console.log(`Thread result: ${await Native.getThreadResult()}`);
     }, 1000);
 });