DCAB v0.19.0

Adds the 30th deterministic paired WordprocessingML fixture.\n\n- New attached-custom-XML-schema namespace rewrite case changes only word/settings.xml.\n- The target-free oracle keeps the declared namespace private and retains fixture schema version 1.\n- Structural validation covers exact leaf shape, member stability, unchanged stored text, deterministic rebuilds, and a DocFence 0.29 adapter integration.