v0.2.42

Fix: dead link for packages whose only submodules are private

Follow-up to v0.2.40/v0.2.41. A package whose only submodules are private/internal (e.g. prefect.cli.deploy) is rendered as a leaf in the navigation tree but written to disk as a …-__init__.mdx page. Navigation emitted the bare leaf path, producing a 404. The leaf branch now points at whichever file was actually written.

Verified against Prefect's full SDK reference: 0 dead links, 0 orphans across all nav entries.

Full changelog: #44