Trigger push_gem workflow after tagging, and allow manual dispatch

Publishing 4.14.0 tagged v4.14.0 and created the GitHub release, but
push_gem.yml did not run and no gem was pushed to RubyGems.

Root cause: GitHub Actions does not trigger downstream workflows for
events driven by GITHUB_TOKEN. script/publish now runs inside the
publish-release workflow, which uses GITHUB_TOKEN for its checkout —
so the 'git push origin v4.14.0' from that job does not fire the
'push: tags: v*' event on push_gem.yml. Previous releases were tagged
by a maintainer running script/publish locally with a PAT, which is
why push_gem always fired for them.

Two changes:

- Add a workflow_dispatch trigger to push_gem.yml with a required
  'tag' input, and check that tag out. This lets a maintainer manually
  push the gem for a specific tag (needed right now to publish v4.14.0
  to RubyGems).
- At the end of script/publish, dispatch push_gem.yml with the freshly
  created tag. || true so any dispatch failure never masks a successful
  release. This makes future releases push the gem automatically even
  when script/publish runs from Actions.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 217f0a0d-a9f2-4607-9643-5fcb3e34f20f

Author: joelhawksley

.github/workflows/push_gem.yml

@@ -4,6 +4,12 @@ on:
   push:
     tags:
       - v*
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Tag to push to RubyGems (e.g. v4.14.0)'
+        required: true
+        type: string
 
 permissions:
   contents: read
@@ -29,6 +35,7 @@ jobs:
 
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1
         with:
+          ref: ${{ github.event_name == 'workflow_dispatch' && inputs.tag || github.ref }}
           persist-credentials: false
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1

script/publish

@@ -71,3 +71,13 @@ gh release create "$tag" \
   --title "$version" \
   --notes "$changelog" \
   --repo ViewComponent/view_component
+
+# Kick off the Push Gem workflow explicitly. GitHub Actions does not
+# trigger downstream workflows for events driven by GITHUB_TOKEN — so
+# the tag push above will not fire push_gem.yml on its own when this
+# script runs inside the publish-release workflow. Dispatch it here so
+# 'script/publish' always results in a gem being pushed to RubyGems.
+gh workflow run push_gem.yml \
+  --repo ViewComponent/view_component \
+  --ref main \
+  --field tag="$tag" || true