DCAB 0.4.0

DCAB 0.4.0 adds external.subdocument_target_retargeted, a deterministic master-document pair where a fixed w:subDoc anchor is retargeted only through word/_rels/document.xml.rels.

The 15-case corpus remains target-free in public truth, preserves fixture schema version 1, and validates the standard external subdocument relationship, exact package boundary, and stable stored text. The optional DocFence adapter maps attached-template and subdocument cases through distinct public dependency counts.

Validation: 12 local tests including the adapter; hosted CI passed on Python 3.11, 3.12, and 3.13; clean wheel and sdist installs validate the bundled corpus.