Two corrections on top of the mention-preservation pick:
- Stripping our own trigger handle from every group message was replaced by never stripping
it in groups, which broke the pre-existing contract that `@bot 2` answers a pending clarify
prompt and `@bot ok` approves (the intercepts match the exact stripped text). Strip only when
no other participant is named; when other bots/users are mentioned the text is kept verbatim
so `@research_bot , @ops_bot …` no longer arrives as `, @ops_bot …`.
- The addressing block carried a per-message fact ("explicitly mentions you: yes/no") inside
`channel_prompt`, which is part of the cached-agent signature: a mention turn followed by a
reply turn rebuilt the AIAgent (prompt-cache miss) every time the shape flipped. Keep only
the username line, byte-identical for the life of the session.
Tests rewritten to pin both contracts (sole-addressee stripping; identical channel_prompt and
agent signature across a mention turn and a reply turn).
bc31e04d83