Trigger math (usage signal, chars/4 estimate fallback, min(80% x window,
250k cap) with overridable knobs), boundary picking that never splits a
turn (user-message starts preferred, iteration starts inside a giant tool
loop), the 8-section summarizer prompt with the continuation contract,
mechanical working-state extraction from tool records, deterministic
user-message preservation, the trim-oldest fallback, outbound-view
application, and context-overflow detection. Injectable provider seam;
no engine changes yet.