fix(actions): show retention info on hover for expired artifacts (#38477)

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>

options/locale/locale_en-US.json

@@ -124,6 +124,7 @@
   "artifacts": "Artifacts",
   "expired": "Expired",
   "artifact_expires_at": "Expires at %s",
+  "artifact_expired_at": "Expired at %s",
   "confirm_delete_artifact": "Are you sure you want to delete the artifact '%s'?",
   "archived": "Archived",
   "concept_system_global": "Global",