Function applyHorizonProfile

applyHorizonProfile(
manifest: Manifest,
options?: { overwrite?: boolean },
): Manifest
Return a copy of the manifest with horizonProfile populated from the article-horizons registry.

Behaviour matrix:
- Slug resolves to a registry entry → horizonProfile is set from buildHorizonProfile.
- Slug is legacy / unknown (no registry entry) AND overwrite is true → any existing horizonProfile is stripped so the "absent for unknown slugs" invariant holds even when the registry evolves (e.g. a slug is removed) or a manifest carries a stale value from a previous registry version.
- Slug is legacy / unknown AND overwrite is false → no-op.
- An existing horizonProfile is present AND overwrite is false → no-op (forward-compat: respect a manifest-supplied value).
The function is pure — the input manifest is never mutated.
Parameters
- manifest: Manifest
  Manifest to enrich.
- options: { overwrite?: boolean } = {}
  Behaviour options.
  - Optional Readonlyoverwrite?: boolean
    When true, replaces (or strips) any existing horizonProfile. Default false.
Returns Manifest
A new manifest with horizonProfile set or removed, or the original manifest reference when no change applies.
- Defined in aggregator/manifest/manifest-writer.ts:77