TemplateLibrary.GetIdByNameAsync was first-row-wins, so a derived slot template
could shadow a same-named base. Now: exact name, base first, derived-only name
only when unique, otherwise unresolved (composition audit says ambiguous).
Tracked-template indexes are base-first too.
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty