ci: trigger goreleaser on tag push, create draft release

[BakerNet]

Problem

Creating a release draft never triggered the goreleaser action. Two reasons:

1. The workflow triggered on the release event, but draft releases do not emit release activity events (draft isn't even a valid type; created doesn't fire for draft saves). release events only fire once a release is published.
2. The config file is named goreleaser.yml (non-standard), and the workflow ran release --clean without --config, so GoReleaser may not have auto-discovered it even if it had triggered.

Change

• Trigger on tag push (push: tags: ['v*']) instead of the release event. This is GoReleaser's canonical setup.
• Create the release as a draft (release.draft: true). GoReleaser builds and uploads all artifacts to a draft; you then generate the changelog in the UI (selecting the previous tag) and publish manually. Publishing last is also required for immutable releases, which freeze a release's assets on publish — uploading to an already-published release would fail.
• Disable GoReleaser's changelog (changelog.disable: true) since notes are generated manually in the UI (GoReleaser's github-native can't pin the previous tag, which is needed for our prerelease/rc tagging).
• Pass --config goreleaser.yml for the non-standard filename.

Release flow after this

1. Push a v* tag → workflow runs, GoReleaser creates a draft release with all binaries/checksums attached.
2. In the UI: Generate release notes, select the previous tag, review.
3. Publish → release is finalized (and frozen, under immutable releases) with assets intact.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request updates the goreleaser.yml configuration to create GitHub releases as drafts and disables automatic changelog generation, allowing for manual changelog creation in the GitHub UI. There are no review comments to address.

[github-actions]

Codeowners approval required for this PR:

• @zbedforrest