Every check-in went through artifact.buildTree from scratch, so a wide tree cost its whole file set per commit against a few changed slices actually written. The converter now applies each check-in's change set over its primary parent's root with TreeEditor — the commit verb's builder — keeps a parent cache released as children consume it, interns the retained cards, runs the pair proof through the run-scoped flatten memo, and parses each source manifest once. The Git importer's LogTreeStore moves to a shared module. Output is unchanged: every check-in hash matches the from-scratch build on libfossil and on a 30k-file synthetic history. Refs zit#167. check-in: 5e0155427e user: dmestas tags: trunk