build: publish PR packages as pre-releases when labeled

When a PR has the "package" label, CI will run `npm pack` and upload
the tarball as a GitHub pre-release.  A separate cleanup workflow
deletes the pre-release when the PR is closed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: arbrandes

.github/workflows/ci.yml

@@ -8,6 +8,10 @@ on:
     branches:
     - '**'
 
+permissions:
+  contents: write
+  pull-requests: write
+
 jobs:
   tests:
     runs-on: ubuntu-latest
@@ -43,3 +47,40 @@ jobs:
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
         fail_ci_if_error: true
+
+    - name: Pack
+      if: contains(github.event.pull_request.labels.*.name, 'package')
+      run: npm pack
+
+    - name: Upload package to a temporary release
+      if: contains(github.event.pull_request.labels.*.name, 'package')
+      env:
+        GH_TOKEN: ${{ github.token }}
+      run: |
+        TAG="pr-${{ github.event.pull_request.number }}"
+        gh release delete "$TAG" --yes --cleanup-tag || true
+        gh release create "$TAG" *.tgz \
+          --prerelease \
+          --title "PR #${{ github.event.pull_request.number }}" \
+          --notes "Test package for PR #${{ github.event.pull_request.number }}"
+
+    - name: Update PR description with package link
+      if: contains(github.event.pull_request.labels.*.name, 'package')
+      env:
+        GH_TOKEN: ${{ github.token }}
+      run: |
+        TAG="pr-${{ github.event.pull_request.number }}"
+        ASSET_URL=$(gh release view "$TAG" --json assets --jq '.assets[0].url')
+
+        gh pr view "${{ github.event.pull_request.number }}" --json body --jq '.body' > /tmp/pr_body.txt
+
+        MARKER_START="<!-- package-link-start -->"
+        MARKER_END="<!-- package-link-end -->"
+
+        if grep -q "$MARKER_START" /tmp/pr_body.txt; then
+          sed -i "/$MARKER_START/,/$MARKER_END/c\\$MARKER_START\n### Latest PR package\n\n$ASSET_URL\n$MARKER_END" /tmp/pr_body.txt
+        else
+          printf '\n%s\n%s\n\n%s\n%s\n' "$MARKER_START" "### Latest PR package" "$ASSET_URL" "$MARKER_END" >> /tmp/pr_body.txt
+        fi
+
+        gh pr edit "${{ github.event.pull_request.number }}" --body-file /tmp/pr_body.txt

.github/workflows/cleanup-pr-packages.yml

@@ -0,0 +1,18 @@
+name: Cleanup PR Package
+
+on:
+  pull_request:
+    types: [closed]
+
+jobs:
+  cleanup:
+    if: contains(github.event.pull_request.labels.*.name, 'package')
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Delete PR release
+      env:
+        GH_TOKEN: ${{ github.token }}
+      run: |
+        TAG="pr-${{ github.event.pull_request.number }}"
+        gh release delete "$TAG" --repo "${{ github.repository }}" --yes --cleanup-tag || true