fix(build): stamp runtime postbuild artifacts

scripts/build-stamp.mjs

@@ -1,44 +1,9 @@
 #!/usr/bin/env node
-import { spawnSync } from "node:child_process";
-import fs from "node:fs";
-import path from "node:path";
 import process from "node:process";
 import { pathToFileURL } from "node:url";
+import { writeBuildStamp } from "./lib/local-build-metadata.mjs";
 
-export function resolveGitHead(params = {}) {
-  const cwd = params.cwd ?? process.cwd();
-  const spawnSyncImpl = params.spawnSync ?? spawnSync;
-  try {
-    const result = spawnSyncImpl("git", ["rev-parse", "HEAD"], {
-      cwd,
-      encoding: "utf8",
-      stdio: ["ignore", "pipe", "ignore"],
-    });
-    if (result.status !== 0) {
-      return null;
-    }
-    const head = (result.stdout ?? "").trim();
-    return head || null;
-  } catch {
-    return null;
-  }
-}
-
-export function writeBuildStamp(params = {}) {
-  const cwd = params.cwd ?? process.cwd();
-  const fsImpl = params.fs ?? fs;
-  const now = params.now ?? Date.now;
-  const distRoot = path.join(cwd, "dist");
-  const buildStampPath = path.join(distRoot, ".buildstamp");
-  const head = resolveGitHead({
-    cwd,
-    spawnSync: params.spawnSync,
-  });
-
-  fsImpl.mkdirSync(distRoot, { recursive: true });
-  fsImpl.writeFileSync(buildStampPath, `${JSON.stringify({ builtAt: now(), head })}\n`, "utf8");
-  return buildStampPath;
-}
+export { BUILD_STAMP_FILE, resolveGitHead, writeBuildStamp } from "./lib/local-build-metadata.mjs";
 
 if (import.meta.url === pathToFileURL(process.argv[1] ?? "").href) {
   try {