Implements DESIGN.md $5.2: the dub-blacklist expression and required-audio
check as policy rules, with the title's original language as a distinct
evaluation input. pt-PT vs pt-BR resolution tries three signals in order
(release-name markers, ffprobe stream strings, container BCP-47 tags) and
emits por-unverified when none settle it, surfacing it as a waiver instead
of guessing.
Closes#11
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>