fix(updates): Prefetch changelog when update is active

[charlesvien]

Problem

Clicking View on the update banner showed a release notes skeleton for a few seconds. The GitHub releases query was gated on the modal being open, so the fetch only started on click even though the app already knew an update was pending.

Changes

• Added a useHasActiveUpdate() selector for the banner-visible update statuses (available, downloading, ready, installing).
• UpdateAvailableModal and WhatsNewModal now enable their releases query as soon as an update is active instead of waiting for open, so the changelog is already in the query cache when clicked. The skeleton now only appears when the data genuinely is not in memory.

How did you test this?

• pnpm --filter @posthog/ui typecheck
• biome check on the updates feature
• Vitest: UpdateBanner and releaseNotes suites (12 passed)

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

[trunk-io]

Merging to main in this repository is managed by Trunk.

• To merge this pull request, check the box to the left or comment /trunk merge below.

After your PR is submitted to the merge queue, this comment will be automatically updated with its status. If the PR fails, failure details will also be posted here

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit c877e6c.}

[greptile-apps]

_{Reviews (1): Last reviewed commit: "prefetch changelog when update is active" | Re-trigger Greptile}

[github-actions]

Small additive UI change that prefetches changelog data when an update is in progress. No showstoppers — the new hook is a simple store selector and the query enable condition change is safe.