refactor(release): move the version-anchor package.json rewrite into the shared lib

Makes the re-anchor file mutation unit-testable alongside the anchor decision.

scripts/__tests__/release-version-anchor.test.mjs

@@ -10,12 +10,16 @@ Regression context: v0.73.0 was cut on `release` while `main` stayed in the
 
 import test from "node:test";
 import assert from "node:assert/strict";
+import { mkdtempSync, readFileSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
 
 import {
   compareReleaseVersions,
   evaluateBetaCycleAnchor,
   isVersionAheadOfStable,
   latestStableVersionFromTags,
+  setPackageJsonVersions,
 } from "../lib/release-version-anchor.mjs";
 
 test("compareReleaseVersions ranks a prerelease below its stable", () => {
@@ -82,3 +86,21 @@ test("isVersionAheadOfStable rejects releases at or below the newest stable", ()
   assert.equal(isVersionAheadOfStable("0.74.0", "0.73.0"), true);
   assert.equal(isVersionAheadOfStable("0.1.0", null), true);
 });
+
+test("setPackageJsonVersions re-anchors only the files that need it", () => {
+  const dir = mkdtempSync(join(tmpdir(), "fusion-anchor-test-"));
+  const root = join(dir, "package.json");
+  const cli = join(dir, "cli.package.json");
+  const missing = join(dir, "nope.package.json");
+  writeFileSync(root, JSON.stringify({ name: "root", version: "0.73.0-beta.6" }, null, 2) + "\n");
+  writeFileSync(cli, JSON.stringify({ name: "cli", version: "0.73.0" }, null, 2) + "\n");
+
+  const rewritten = setPackageJsonVersions([root, cli, missing], "0.73.0");
+
+  // Already-anchored and absent files are left alone; the stale one is rewritten.
+  assert.deepEqual(rewritten, [root]);
+  assert.equal(JSON.parse(readFileSync(root, "utf8")).version, "0.73.0");
+  assert.equal(JSON.parse(readFileSync(cli, "utf8")).version, "0.73.0");
+  // Unrelated fields survive the rewrite.
+  assert.equal(JSON.parse(readFileSync(root, "utf8")).name, "root");
+});

scripts/lib/release-version-anchor.mjs

@@ -14,6 +14,8 @@ and the dev checkout (`pnpm dev`, dashboard version badge) still reported the
 last beta.
 */
 
+import { existsSync, readFileSync, writeFileSync } from "node:fs";
+
 /**
  * Prerelease-aware semver comparison: returns <0, 0, >0.
  * `1.2.3-beta.1` sorts BELOW `1.2.3`; numeric prerelease identifiers compare
@@ -91,6 +93,27 @@ export function evaluateBetaCycleAnchor({ cycleBase, latestStable }) {
   return { stale, anchor: stale ? latestStable : cycleBase };
 }
 
+/**
+ * Point each package.json at `version`, skipping files already there or absent.
+ * Used to re-anchor the fixed group (plus the workspace root) on the shipped
+ * stable before `changeset pre enter`, which snapshots these versions into
+ * pre.json's `initialVersions` and derives every X.Y.Z-beta.N from them.
+ *
+ * @returns {string[]} the paths actually rewritten, so a dry-run can restore them.
+ */
+export function setPackageJsonVersions(paths, version) {
+  const rewritten = [];
+  for (const path of paths) {
+    if (!existsSync(path)) continue;
+    const pkg = JSON.parse(readFileSync(path, "utf8"));
+    if (pkg.version === version) continue;
+    pkg.version = version;
+    writeFileSync(path, JSON.stringify(pkg, null, 2) + "\n");
+    rewritten.push(path);
+  }
+  return rewritten;
+}
+
 /**
  * Backstop applied to both channels: a release must be strictly newer than the
  * newest published stable. Catches hand-edited pre.json, a back-merge resolved

scripts/release.mjs

@@ -52,6 +52,7 @@ import {
   evaluateBetaCycleAnchor,
   isVersionAheadOfStable,
   latestStableVersionFromTags,
+  setPackageJsonVersions,
 } from "./lib/release-version-anchor.mjs";
 import {
   archivePointerLine,
@@ -418,24 +419,12 @@ function readFixedGroupPackageNames() {
  * Returns the list of rewritten paths so a dry-run can restore them.
  */
 function rewriteFixedGroupVersions(version) {
-  const rewritten = [];
+  const paths = ["package.json"];
   for (const name of readFixedGroupPackageNames()) {
     const dir = findPackageDir(name);
-    if (!dir) continue;
-    const pkgPath = join(dir, "package.json");
-    const pkg = JSON.parse(readFileSync(pkgPath, "utf8"));
-    if (pkg.version === version) continue;
-    pkg.version = version;
-    writeFileSync(pkgPath, JSON.stringify(pkg, null, 2) + "\n");
-    rewritten.push(pkgPath);
+    if (dir) paths.push(join(dir, "package.json"));
   }
-  const rootPkg = JSON.parse(readFileSync("package.json", "utf8"));
-  if (rootPkg.version !== version) {
-    rootPkg.version = version;
-    writeFileSync("package.json", JSON.stringify(rootPkg, null, 2) + "\n");
-    rewritten.push("package.json");
-  }
-  return rewritten;
+  return setPackageJsonVersions(paths, version);
 }
 
 /**