A long multi-turn session driven through the real SessionManager with a
forced 3k-token cap: repeated compactions advance the boundary, later
summaries fold the previous one in, the provider verifiably receives the
compacted view (summary block + verbatim tail, bounded) while the
canonical transcript keeps every turn, state survives a mid-conversation
rebuild, and the persisted record round-trips the final boundary.
Scripted stand-in for the live-model smoke: intent survival across a
real summarizer (prompt tuning) still needs a configured provider key.
