Add PR preview builds with Cloudflare preview URLs

.github/workflows/pr-preview.yml

@@ -0,0 +1,95 @@
+# Builds every PR and uploads the result to Cloudflare as a Worker *version* —
+# a preview that leaves production untouched — then comments the preview URL on
+# the PR. Complements Workers Builds, which deploys `main` to production but
+# reports nothing back to GitHub.
+#
+# Requires two repository secrets:
+#   CLOUDFLARE_API_TOKEN  — API token with Workers Scripts: Edit on the account
+#   CLOUDFLARE_ACCOUNT_ID — the Cloudflare account id
+# Until they are set (and on fork/Dependabot PRs, which cannot read secrets),
+# the build still runs as a check and the preview upload is skipped with a note.
+name: PR preview
+
+on:
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: pr-preview-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  preview:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version-file: .node-version
+          cache: npm
+
+      - run: npm ci
+
+      - run: npx astro build
+
+      - name: Check for Cloudflare credentials
+        id: creds
+        env:
+          CLOUDFLARE_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+        run: |
+          if [ -n "$CLOUDFLARE_API_TOKEN" ]; then
+            echo "available=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "available=false" >> "$GITHUB_OUTPUT"
+            echo "CLOUDFLARE_API_TOKEN is not available (missing secret, fork PR, or Dependabot) — preview upload skipped." >> "$GITHUB_STEP_SUMMARY"
+          fi
+
+      - name: Upload preview version to Cloudflare
+        if: steps.creds.outputs.available == 'true'
+        id: upload
+        uses: cloudflare/wrangler-action@v3
+        with:
+          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
+          command: versions upload
+
+      - name: Comment the preview URL on the PR
+        if: steps.creds.outputs.available == 'true'
+        uses: actions/github-script@v7
+        env:
+          WRANGLER_OUTPUT: ${{ steps.upload.outputs.command-output }}
+        with:
+          script: |
+            const match = (process.env.WRANGLER_OUTPUT || '').match(/https:\/\/\S+\.workers\.dev/);
+            const marker = '<!-- workers-preview-comment -->';
+            const sha = context.payload.pull_request.head.sha.slice(0, 7);
+            const body = match
+              ? `${marker}\n### 🔍 Preview\n\n**${match[0]}**\n\nBuilt from \`${sha}\`. Uploaded as a Worker version — production is unaffected until merge.`
+              : `${marker}\n### 🔍 Preview\n\nThe preview version uploaded, but no preview URL appeared in the wrangler output — check that the worker's Preview URLs setting is enabled. Built from \`${sha}\`.`;
+            const { data: comments } = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              per_page: 100,
+            });
+            const existing = comments.find((c) => c.body && c.body.includes(marker));
+            if (existing) {
+              await github.rest.issues.updateComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: existing.id,
+                body,
+              });
+            } else {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.issue.number,
+                body,
+              });
+            }