system[1] delta channel

Chose a session-frozen LTM baseline in system[1] plus user→assistant delta updates over the former changing system[2] because mutating system prefixes breaks prompt-cache stability. system[0] holds stable harness rules; system[1] is the one-hour cache-write anchor; context changes remain in the volatile tail and are re-pinned only when material. Delta placement follows [[01a0a06d-058c-7a46-a251-5aea6e25dbc7]].