Context Lifecycle Management

Treating an agent's active context as indexed runtime objects with a lifecycle (fold/mask/prune, recoverable sidecars, cache-aware commit) rather than a token buffer to trim — Xiaohongshu's Self-GC is the measured treatment (~44% prefix pruning at ~85% no-impact), plus the five-primitive taxonomy, the O(n²) full-append cost case, and RCWT's coordination-share cliff.