`@s.SourceHash[..12]` on an unvalidated nvarchar(64) threw out of
BuildRenderTree and took the whole /scripts page to an HTTP 500. Replaced with a
shared, null/short-safe `DisplayText.Abbreviate`, applied to all five unguarded
range-operator slices over DB-sourced strings in the AdminUI.
Live-verified on docker-dev: /scripts 500 -> 200 with the short hashes rendered
in full; long hashes still truncate with an ellipsis on the other pages.
Joseph Doherty