Covers what it does, the head/tail protection, the cursor and rolling
summary, defrag, how the session DB is kept in step, and the failure
paths. States the tradeoff up front: compression cost is amortized across
turns, at the price of older detail becoming summarized earlier in a
session than batch-only compaction would.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
