Add Find command family

[maniramezan]

Summary

• add a portable typed Find expression model
• support roots, names, paths, file types, depth predicates, boolean composition, print, and print0
• safely handle ambiguous roots and avoid shell-exec expression APIs
• add trait wiring, tests, DocC, CI, and agent guidance

Validation

• 404 all-traits tests
• coverage 90.51%
• strict formatting, trait and DocC validators
• DocC generation