Add a temporary diagnostic job that reports, on canonical pipelines,
whether a consumer's fairway_manifest input already equals
runway_dir/fairway.yaml. On a mismatch it prints agent-actionable fix
steps (move the manifest, set the input) so the discrepancy can be
resolved with a follow-up merge request.

This de-risks the planned consolidation where the Fairway manifest is
standardized under the runway directory and derived from runway_dir,
letting the explicit fairway_manifest input be dropped. Also add the
runway_dir input (default .runway) used by that path.

The job is informational (allow_failure) and runs only on canonical,
gated to the Fairway path. It is temporary and should be removed once
the manifest location is consolidated.

See !1572

AI-assisted: Claude Code (Claude Opus 4.8)

feat(release-platform): add fairway manifest path check

See merge request !1608

## [4.13.0](https://gitlab.com/gitlab-com/gl-infra/common-ci-tasks/-/compare/...) (2026-06-16)

### Features

* **release-platform:** add fairway manifest path check ([faea6681](faea6681))