docs(changelog): add new entries from changelog

[windmill-internal-app]

This PR adds new changelog entries.

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Summary by cubic

Adds a new changelog entry to the sidebar for “Pipelines with asset lineage, partitions and joins.”
Includes the link to https://www.windmill.dev/changelog/pipelines and the date 2026-05-16.

^{Written for commit b4968c7. Summary will update on new commits.}

[cloudflare-workers-and-pages]

Deploying windmill with    Cloudflare Pages

Latest commit:	b4968c7
Status:	✅  Deploy successful!
Preview URL:	https://207f1168.windmill.pages.dev
Branch Preview URL:	https://changelog-update-28380481478.windmill.pages.dev

View logs

[github-actions]

Pi Review

Good to merge

This PR adds a single changelog entry (Pipelines with asset lineage, partitions and joins) to the sidebar changelog list. The entry follows the existing format (label, href, date) and is placed at the top of the list maintaining reverse chronological order. No code logic, security, or AGENTS.md issues.

Test coverage

CI / docs-only change — no automated tests expected. The changelog entry can be manually verified by loading the Windmill frontend and confirming the new entry appears in the sidebar changelog section.

[github-actions]

Codex Review

cc @windmill-internal-app[bot]
Mergeable, but should ideally address nits: broken changelog link

Found 1 issues:

1. [P2] The newly added changelog entry links to a 404. https://www.windmill.dev/changelog/pipelines returns 404 on both HEAD and GET, so users clicking this sidebar changelog item will land on a missing page.
   frontend/src/lib/components/sidebar/changelogs.ts:10

Test coverage
No automated tests expected for this frontend changelog data-only update. Manual verification should click the new sidebar changelog item and confirm it opens the intended published changelog page with a 200 response.