Add a Testcontainers test that re-imports a document with a receiver and a tag
removed from the canonical row and asserts both links are pruned. Add a test that a
register person referenced by a document row is never flipped to provisional,
regardless of re-import, since the orchestrator loads the register/tree before
documents and the monotonic-downward guard prevents a flip. Pin that cross-loader
precedence in a mergeCanonical comment.
Refs #669
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>