Fix: Empty changelog groups, silent-skip on empty release, and publish race

[tajobe]

Summary

• changelog.groups is now empty instead of the plugin's default 6-item Keep a Changelog list, so patchChangelog no longer stubs out empty ### Added / ### Changed / ... headers in every new Unreleased section.
• Set patchEmpty = false on the patchChangelog task invoked from the release hook. Previously, if Unreleased had no content at release time, PatchChangelogTask threw StopActionException, which — since we call .run() directly instead of through Gradle's task graph — got silently swallowed, making the entire release a silent no-op (no commit, no tag, no push) while reporting BUILD SUCCESSFUL. Now it throws MissingReleaseNoteException, a real failure with a clear message.
• publish-workflow.yml triggers on both the branch push and the tag push from the same release, so two Publish runs fired concurrently and both tried to gradlew publish the same version — one 409s. Added a check-tag step and gated the Gradle Publish step to skip on the branch-triggered run when it's also sitting on a release tag, so only the tag-triggered run publishes.

Test plan

• ./gradlew clean build passes
• Verified groups = emptyList() in an isolated worktree via release.localOnly: the new Unreleased section has no stub headers, and existing Unreleased content correctly moved into the new version section (confirmed via git show diff on the resulting local commit)
• Verified patchEmpty = false in an isolated worktree: with an empty Unreleased section, the release now fails loudly with MissingReleaseNoteException instead of silently producing no commit/tag/push while reporting success
• publish-workflow.yml YAML syntax validated; the if: condition logic matches the described skip case (branch run + on a release tag) directly

[Copilot]

Pull request overview

This PR improves the release/publish automation around changelog patching and GitHub Packages publishing, addressing empty changelog group stubs, silent release skipping when Unreleased is empty, and duplicate publish attempts from concurrent workflow triggers.

Changes:

• Stop pre-populating new Unreleased sections with default Keep a Changelog group headers by setting changelog.groups to empty.
• Make the release hook fail loudly when Unreleased has no content by setting patchEmpty = false on the invoked patchChangelog task.
• Add tag-detection and gating in the publish workflow to avoid duplicate publishes when both branch and tag pushes trigger concurrently.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.

File	Description
CHANGELOG.md	Updates Unreleased notes to reflect the release/publish automation fixes.
build.gradle.kts	Adjusts changelog plugin configuration and makes empty-Unreleased releases fail loudly.
.github/workflows/publish-workflow.yml	Attempts to prevent duplicate publishes by skipping publish on the branch-triggered run when a release tag is present.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.