2.0.0 — catalog overhaul

Switches the catalog onto current GitLab CI idioms. Backward
incompatible against v1.x consumer overrides; v1.x consumers stay
on @v1.x until ready to migrate.

Highlights:
- spec:component + $[[ component.version ]] image pinning (true
  tooling coupling; no more silent :latest drift)
- new go-lint template (replaces docker.io/golangci-lint pull cap +
  allow_failure pattern)
- new ci-runtime-go runtime image (UBI micro 9.6) for Go CLI
  release containers via from_artifacts mode
- container-image: from_artifacts (byte-for-byte parity with signed
  binary), multi_arch (amd64+arm64 manifest list), sign_image
  (cosign by registry digest, --recursive for manifest lists),
  binfmt preflight check, BUILDAH_FORMAT=oci default
- go-build + go-release-binary: parallel:matrix cross-compile
  (linux/amd64, linux/arm64, darwin/arm64), per-target Go module
  cache, per-binary .sha256 sidecars
- input validation: regex on cosign_version, syft_version,
  golangci_lint version, image_tag, model name
- workflow:auto_cancel guidance; interruptible:true on build jobs,
  interruptible:false on release-stage jobs
- catalog meta-pipeline now publishes ci-go/ci-rust/ci-runtime-go/ci
  at :\$CI_COMMIT_TAG on every catalog tag
- ci-go and ci-rust Containerfiles pull FROM mirror.gcr.io
- renovate.json gains customManager regex for ARG version pins
- README backfilled with go-* and rust-* sections; recommended
  consumer pipeline shape
- CHANGELOG.md (new) in Keep a Changelog format

Tag convention: v1.x stays v-prefixed (frozen historical records);
2.0.0+ is unprefixed strict semver per GitLab catalog convention.

See CHANGELOG.md for full migration guide.