fix(release): apply PSR v10.5.3 bug mitigations to reusable workflow (#184)

PSR v10.5.3 has two bugs affecting the no-PyPI release pattern:

1. 422 on GitHub Release creation: github3 library serializes draft/prerelease
   as JSON strings rather than booleans. Fix: vcs_release: "false" + separate
   gh release create step that types booleans correctly.

2. Detached HEAD prevents branch matching: actions/checkout with ref: <sha>
   leaves HEAD detached; PSR needs an attached branch to match branches config.
   Fix: git checkout -B "$HEAD_BRANCH" after checkout.

Also adds:
- Fork verification step for workflow_run callers (S7631)
- SHA-pinned checkout (ref: workflow_run.head_sha || github.sha)
- commit: "false" so PSR only pushes tags (branch rulesets exempt tag refs)
- publish-to-pypi default changed from true to false

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: williaby

.github/workflows/python-release.yml

@@ -66,7 +66,7 @@ on:
         description: 'Publish to PyPI after release'
         required: false
         type: boolean
-        default: true
+        default: false
       pypi-package-name:
         description: 'PyPI package name'
         required: false
@@ -249,6 +249,17 @@ jobs:
         with:
           egress-policy: audit
 
+      - name: Verify trusted workflow_run source
+        if: github.event_name == 'workflow_run'
+        env:
+          HEAD_OWNER: ${{ github.event.workflow_run.head_repository.owner.login }}
+          REPO_OWNER: ${{ github.repository_owner }}
+        run: |
+          if [ "$HEAD_OWNER" != "$REPO_OWNER" ]; then
+            echo "::error::Refusing: triggering workflow originated from a fork (owner: $HEAD_OWNER)"
+            exit 1
+          fi
+
       - name: Validate skip-tests opt-out
         if: ${{ !inputs.run-tests }}
         env:
@@ -266,6 +277,16 @@ jobs:
         with:
           fetch-depth: 0
           token: ${{ github.token }}
+          ref: ${{ github.event.workflow_run.head_sha || github.sha }}
+
+      - name: Attach HEAD to branch
+        if: github.event_name == 'workflow_run'
+        env:
+          HEAD_BRANCH: ${{ github.event.workflow_run.head_branch }}
+        run: |
+          # Checking out a SHA leaves the repo in detached HEAD state.
+          # PSR needs an attached branch to match against branches config.
+          git checkout -B "$HEAD_BRANCH"
 
       - name: Set up Python
         uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405  # v6.2.0
@@ -347,6 +368,15 @@ jobs:
           git_committer_name: "github-actions[bot]"
           git_committer_email: "github-actions[bot]@users.noreply.github.com"
           force_level: ${{ inputs.force-release }}
+          # Branch ruleset blocks direct commits; tag refs are exempt. Skipping
+          # the version-bump commit means PSR only pushes a tag, which succeeds
+          # without any bypass actor.
+          commit: "false"
+          # PSR v10.5.3 serializes draft/prerelease as JSON strings ("false")
+          # instead of booleans, which GitHub's Releases API rejects with 422.
+          # Release creation is handled by the step below via gh, which types
+          # booleans correctly.
+          vcs_release: "false"
 
       - name: Sign artifacts with Sigstore
         if: ${{ inputs.sign-artifacts && (steps.semantic-release.outputs.released == 'true' || !inputs.semantic-release) }}
@@ -355,12 +385,17 @@ jobs:
           inputs: ./dist/*.tar.gz ./dist/*.whl
           release-signing-artifacts: true
 
-      - name: Upload to GitHub Release (Semantic)
+      - name: Create GitHub Release
         if: ${{ inputs.semantic-release && steps.semantic-release.outputs.released == 'true' }}
-        uses: python-semantic-release/publish-action@310a9983a0ae878b29f3aac778d7c77c1db27378  # v10.5.3
-        with:
-          github_token: ${{ github.token }}
-          tag: ${{ steps.semantic-release.outputs.tag }}
+        env:
+          GH_TOKEN: ${{ github.token }}
+          TAG: ${{ steps.semantic-release.outputs.tag }}
+        run: |
+          gh release create "$TAG" \
+            --title "$TAG" \
+            --generate-notes \
+            --repo "$GITHUB_REPOSITORY" \
+            dist/*
 
       # Manual Release Mode
       - name: Manual Release