The artifact info hover tooltip (#37100) only worked for live artifacts.
Hovering an expired/deleted artifact showed nothing, and even on live
artifacts the retention date was missing on real runs.
Two root causes:
1. **Expired artifacts had no tooltip.** In the run view sidebar,
expired artifacts render in a separate branch that omitted
`data-tooltip-content` entirely, so there was nothing to hover.
2. **`ExpiresUnix` was no longer sent.** The `ActionRunAttempt` refactor
(#37119) dropped `ExpiresUnix` from `fillViewRunResponseArtifacts`, so
real runs always returned `0` and the tooltip fell back to size-only.
Only the devtest mock still populated it, which masked the regression.
Artifacts without a recorded expiry (`expiresUnix <= 0`) still degrade
gracefully to a size-only tooltip. Both states can be previewed on the
`/devtest/mock/*` actions run page.
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
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