Reads the optional `generation` integer from the canonical tree JSON and
routes it into PersonUpsertCommand. Out-of-range values are skip-and-
warned with the same policy as the register importer.
Tree imports run after register (per CanonicalImportOrchestrator); a
tree-confirmed integer overwrites a register-parsed value — both sides
are "canonical" in preferHuman terms (neither is a human edit).
Refs #689
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>