Identify and Delete All Zombie Files Across Repos

Per docs-doctrine anti-zombie rule: a file is a zombie if it is not referenced, not canonical, and not generated. Zombies must be deleted immediately. Files must not linger in "unused but present" state.

Acceptance Criteria

• [ ] Scan all managed repos for files that are not referenced by any other file
• [ ] Cross-check against canonical registry — exclude files that are canonical sources
• [ ] Cross-check against generation manifests — exclude files that are actively generated
• [ ] Produce a zombie candidate list for review
• [ ] Delete confirmed zombies (with VCS history preserved)
• [ ] Verify zero zombie files remain after cleanup