Phase 2 T46 pinned the witness mask contract on search_memories with a
witness_role parameter (host/guest/you). The prompt-assembly call site
in assemble_narrative_prompt was hardcoded to "host", which silently
returned the wrong rows when the speaker was the guest bot.
Derive the witness role from chat membership via a new private helper
_witness_role_for(speaker_bot_id, host_bot_id), and apply it at the
search_memories call. Behaviour is identical when the speaker is the
host (or when no guest is present); the fix is load-bearing only when
the guest bot is the speaker — exactly the scenario Phase 2 T43 added
support for.
Tests: pin both directions (host-as-speaker and guest-as-speaker) by
patching the imported search_memories reference and asserting the
witness_role argument the call site emits.
Joseph Doherty