build(serialization): move bundle banner into build.mjs (no // in package.json)

The build script's --banner put a `//` comment string inside package.json; move
bundling into crates/runtime/js/build.mjs (Bun.build API) so package.json stays
comment-free. Output is unchanged.

Author: Thanga-Ganapathy

crates/runtime/js/build.mjs

@@ -0,0 +1,19 @@
+// Bundles serialization/index.ts into the embedded runtime module
+// crates/runtime/src/runtime_modules/serialization.js. Run: bun run build
+const BANNER = "// @generated by `bun run build` in crates/runtime/js — do not edit by hand.\n";
+const OUT = new URL("../src/runtime_modules/serialization.js", import.meta.url);
+
+const result = await Bun.build({
+  entrypoints: [new URL("./serialization/index.ts", import.meta.url).pathname],
+  format: "esm",
+  target: "node",
+});
+
+if (!result.success) {
+  for (const log of result.logs) console.error(log);
+  process.exit(1);
+}
+
+const code = await result.outputs[0].text();
+await Bun.write(OUT, BANNER + code);
+console.log("wrote", OUT.pathname, `(${(BANNER.length + code.length)} bytes)`);

crates/runtime/js/package.json

@@ -4,7 +4,7 @@
   "type": "module",
   "description": "Source for the runtime:serialization module — pure-JS Protobuf (reflection) + thin wrappers over the Rust-backed text/binary parser ops. Bundled into crates/runtime/src/runtime_modules/serialization.js.",
   "scripts": {
-    "build": "bun build serialization/index.ts --format=esm --target=node --banner='// @generated by `bun run build` in crates/runtime/js — do not edit by hand.' --outfile=../src/runtime_modules/serialization.js",
+    "build": "bun build.mjs",
     "test": "bun test"
   },
   "devDependencies": {

crates/runtime/src/runtime_modules/serialization.js

@@ -1,5 +1,4 @@
 // @generated by `bun run build` in crates/runtime/js — do not edit by hand.
-
 // serialization/protobuf/lexer.ts
 var IDENT_START = /[A-Za-z_]/;
 var IDENT_PART = /[A-Za-z0-9_]/;