When a collection or threshold change can't be tied to an addon, name the
last game event seen (or 'no recent event' after 5 s) in the debug line and
in /ggc, to help tell client mods and the game from real addons.
Adds tests/test_unknown_context.lua.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019W3rwtugSE5NbbiWQCbbKX
