fix: stamp the tenant on documents added with AddRange (#29)

MultiTenancyInterceptor read operation.CurrentDocument, which AddRangeOperation
leaves null — it carries its documents in CurrentDocuments instead. So a range
insert was stamped with nothing: the rows went in with no tenant on them, and
the query filter then hid them from every read that followed. The row is there,
nothing can see it, and nothing failed.

Both shapes are read now. Add is unchanged; AddRange gets the same rule, which
includes leaving an already-set tenant alone.


Claude-Session: https://claude.ai/code/session_018ZVpvVJ5YGPvzAhvS3Ue5o

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>