ci: add release-major-tag workflow (#552)

* build: drop docker-bake in favor of plain npm

Every TypeScript action maintained by actions/* (checkout, setup-node,
setup-go, cache, upload-artifact) uses plain npm scripts. The bake
setup is a docker/* org convention and adds friction for TS work:
contributors need Docker, the dev loop is ~10x slower than npm, and
Alpine-vs-host byte drift in dist/index.js makes PRs bounce.

Replace with the standard pattern:
- .node-version pins Node 24 so contributors and CI agree
- npm scripts (build, lint, format, test, pre-checkin) replace bake
  targets one-for-one
- validate.yml runs lint + a check-dist diff (mirrors actions/setup-node)
  and a vendor check that npm install --package-lock-only is a no-op
- test.yml uses setup-node + sigstore/cosign-installer, drops bake-action
- dependabot-build.yml regenerates dist via npm instead of bake

CONTRIBUTING.md and README development section updated to match.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* build: align scripts and workflows with actions/* convention

Match the standard layout used by actions/checkout, actions/setup-node,
etc.:

- package.json scripts: split format/format-check (Prettier) from
  lint/lint:fix (ESLint), and have pre-checkin run all four (format,
  lint:fix, build, test) in that order.
- validate.yml lint job runs format-check + lint as separate steps.
- test.yml drops the redundant --coverage flag (now in the test script).
- Drop dependabot-build.yml: actions/* don't auto-rebuild dist on
  dependabot PRs; the check-dist style validate / build job catches
  drift and a maintainer rebuilds locally if needed.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* ci: add release-major-tag workflow

Adopts the actions/checkout pattern (workflow_dispatch with target +
major_version inputs that force-pushes the major tag). Doubles as a
rollback tool. Documented in CONTRIBUTING under a 'Releasing' section.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* ci: drop irrelevant pin comment from release-major-tag

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

CONTRIBUTING.md

@@ -72,3 +72,18 @@ Use [Conventional Commits](https://www.conventionalcommits.org/) (`feat:`,
 - The `signing` CI job and `goreleaser-pro` matrix entries are skipped on PRs
   from forks because they need repository secrets — that's expected and not
   something you need to fix.
+
+## Releasing (maintainers)
+
+1. Create a new GitHub Release with a semver tag (e.g. `v7.1.0`) — either
+   through the UI or `gh release create v7.1.0 --generate-notes`.
+2. Once the release exists, run the [**release major tag**](./.github/workflows/release-major-tag.yml)
+   workflow from the Actions tab:
+   - `target`: the new tag (e.g. `v7.1.0`)
+   - `major_version`: the major version to repoint (e.g. `v7`)
+
+   This force-pushes the major tag to the new release so consumers using
+   `goreleaser/goreleaser-action@v7` pick up the change.
+
+   The same workflow doubles as a rollback tool — pass an older tag as
+   `target` to revert the major.