Hub pages 4/4: {whats-new}

[florent-leborgne]

Part 4 of 4, based on #3827. Implements elastic/docs-content-internal#1383.

Demo: https://docs-v3-preview.elastic.dev/elastic/docs-builder/pull/3829/examples/products/docs-builder

A recency panel for a hub page. A reader who bookmarks a hub wants a quick answer to "what changed recently" without hunting through release notes.

With this merged, docs/examples/products/docs-builder.md is a complete hub page.

Usage

One line for the common case:

:::{whats-new}
:product: docs-builder
:::

Omitting :product: accepts the same schema as an inline YAML body, for a one-off panel.

Implementation choices

The panel content lives in the content repository. The prototype reads config/whats-new.yml from docs-builder, so a writer editing a highlight card opens a pull request against the build tool and waits for a release. It now reads hub-whats-new.yml from the root of the current documentation set, beside changelog.yml and redirects.yml.

That makes the directive documentation-set scoped. It cannot render another repository's panel, and no syntax would fix it. Cross-link resolution maps pages through the link index, and a YAML data file is not a page. In an isolated build the other repository is not checked out, so there is no file to read. Every hub page lives in the same repository as its content file, so this costs nothing today. elastic/docs-content-internal#1383 has been updated to drop the earlier claim that any page could render any product's panel.

Three schema fields are removed. items[].meta and the top-level badge are in the prototype's schema but no view reads them. An option that renders nothing is worse than no option. items[].badge is removed too: a badge reading "New" inside a What's new panel is redundant, and tag already carries per-item categorisation.

Machine-readable output. The LLM export keeps the date and tag alongside each title, which is what a reader asking "what changed recently" wants. The search body gets nothing, as with the other hub directives.

Example content

docs/hub-whats-new.yml uses every remaining field once, including two release-links and an upgrade-link, so it can be copied and trimmed. It carries five items, which fills the three-column grid cleanly alongside the two-column featured card.

Follow-up, not in this change

A skill in docs-content that updates hub-whats-new.yml from the release notes of each product with a hub page. It should read the changelog YAML bundles rather than rendered pages, since those are structured and already feed release notes.

Testing

./build.sh unit-test passes. dotnet format and npm run fmt:check are clean. A full docs build reports 0 errors and 0 warnings.

tests/authoring/Blocks/Hub/WhatsNew.fs covers the inline-body path, the featured card spanning two columns, release and upgrade links, and three failure paths including an unresolvable product key.

Screenshots to add or update

None attached. The five-card grid with its featured span is worth checking on the preview.