Add local-publish script for the Node package

nodejs/scripts/publish.mjs builds the wasm (wasm-pack), runs the smoke test,
then `npm publish` to a configurable registry (default a local one at
http://localhost:4873; override via --registry= or NPM_REGISTRY). Supports
--dry-run. Wired as `npm run publish:local`.

nodejs/package.json

@@ -15,6 +15,7 @@
   "scripts": {
     "build": "wasm-pack build --target nodejs --out-dir pkg",
     "test": "node test.js",
+    "publish:local": "node scripts/publish.mjs",
     "prepublishOnly": "npm run build"
   },
   "keywords": ["svg", "vectorization", "raster", "wasm", "computer-graphics"],

nodejs/scripts/publish.mjs

@@ -0,0 +1,42 @@
+#!/usr/bin/env node
+// Build the wasm package and publish it, by default to a local npm registry
+// (e.g. a Verdaccio instance at http://localhost:4873).
+//
+//   node scripts/publish.mjs                       # publish to the local registry
+//   node scripts/publish.mjs --dry-run             # build + pack, don't publish
+//   node scripts/publish.mjs --registry=http://... # override the registry
+//   NPM_REGISTRY=http://... node scripts/publish.mjs
+//
+// The registry may also be given via the NPM_REGISTRY env var.
+
+import { execFileSync } from 'node:child_process';
+import { fileURLToPath } from 'node:url';
+import { dirname, resolve } from 'node:path';
+
+const pkgDir = resolve(dirname(fileURLToPath(import.meta.url)), '..');
+
+const args = process.argv.slice(2);
+const dryRun = args.includes('--dry-run');
+const regArg = args.find((a) => a.startsWith('--registry='));
+const registry =
+  (regArg && regArg.slice('--registry='.length)) ||
+  process.env.NPM_REGISTRY ||
+  'http://localhost:4873';
+
+function run(cmd, cmdArgs) {
+  console.log(`\n$ ${cmd} ${cmdArgs.join(' ')}`);
+  execFileSync(cmd, cmdArgs, { stdio: 'inherit', cwd: pkgDir });
+}
+
+// 1. Fresh wasm build (regenerates pkg/).
+run('wasm-pack', ['build', '--target', 'nodejs', '--out-dir', 'pkg']);
+
+// 2. Sanity check before publishing.
+run('node', ['test.js']);
+
+// 3. Publish (or dry-run) to the chosen registry.
+const publishArgs = ['publish', '--registry', registry];
+if (dryRun) publishArgs.push('--dry-run');
+run('npm', publishArgs);
+
+console.log(`\n✔ ${dryRun ? 'dry-run for' : 'published to'} ${registry}`);