DCAB 0.17.0

Adds a deterministic mail-merge recipient-selection fixture that changes only one stored recipient inclusion state in a complete internal recipient-data topology.

The corpus now contains 28 paired cases. Fixture schema version 1 and the target-free observation envelope remain unchanged. Validation, independent python-docx/OPC loading, DocFence 0.27 strict scoring, wheel installation, and sdist installation all passed.