ci: fail the pull request whose changeset would generate an unformatted changelog

.changeset/web-embed-on-core.md

@@ -3,7 +3,6 @@
 ---
 
 **Your pages are now ready for AI agents.** While the editor is open, an agent in your visitor's browser (ChatGPT's browser, Chrome with WebMCP) can read and fill the form, move between pages and submit it, with the same permissions as any other integration. It is on by default: add `webmcp="false"` to the script tag to turn it off.
-
 - **More PDF links open in SimplePDF**: `Report.PDF`, `form.pdf?v=2` and `guide.pdf#page=3` used to open in the browser.
 - **Japanese and Dutch**: pages in either language open the editor in that language.
 - **Stored documents open directly**: a link to a SimplePDF document (`/documents/<id>`) opens it in the editor.

.github/workflows/changelog-check.yaml

@@ -0,0 +1,42 @@
+name: Changelog Check
+
+on:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - .changeset/**
+      - package.json
+      - embed/**
+      - react/**
+      - web/**
+
+jobs:
+  check:
+    name: Generated changelogs are formatted
+    runs-on: ubuntu-latest
+    # The version PR itself is checked by each package's Formatting job.
+    if: github.head_ref != 'changeset-release/main'
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: "24"
+
+      - name: Install dependencies
+        run: npm ci
+
+      # The version PR is pure `changeset version` output. Running it here, then the formatting
+      # checks the version PR runs, fails the pull request that adds a changeset whose generated
+      # CHANGELOG is not formatted, so the release never needs a fix.
+      - name: Generate the changelogs the release will write
+        run: npm run version
+
+      - name: Check they are formatted
+        run: |
+          npm run --prefix react test:format
+          npm run --prefix web test:format

package.json

@@ -8,7 +8,7 @@
   ],
   "scripts": {
     "changeset": "changeset",
-    "version": "changeset version && npm run --prefix react format",
+    "version": "changeset version",
     "publish": "changeset publish"
   },
   "devDependencies": {