Add paths-ignore (docs/**, **/*.md) to the gate's push + pull_request
triggers so markdown/docs-only changes don't run a full clippy+test that
can't change the outcome. Mixed code+docs pushes still gate (not all
files are ignored); flake/toolchain changes are deliberately not ignored.
Also refresh a stale ADR-0049 -> ADR-ci-002 comment reference.
Tag pushes ignore paths: filters, so a release tag spuriously rebuilt
the unchanged CI image and re-ran the gate on a commit the branch push
already gated. Add branches: ['**'] to both push triggers — tag pushes
no longer fire them (release.yaml owns tags). Pushing commits + a tag
together still gates the commits via the branch push.