The stateReason field was added in GHES ~3.4, which is far older than
the earliest supported GHES version (3.14). The feature detection and
conditional inclusion of stateReason is therefore unnecessary.
This removes:
- StateReason field from IssueFeatures struct
- GHES introspection query in IssueFeatures() (only ActorIsAssignable
remains, which is always false on GHES)
- Conditional stateReason field inclusion in issue list
- Feature detection guard in issue close
- Feature detection guard in FindIssueOrPR
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>