v0.6.3

Fixed

• audit_note.py exempts the overview segment from the transcript-coverage
  gate. That segment's transcript is every other segment's concatenated, so a
  one-page catalog scores about 0.01 against a 0.1 floor and can never pass —
  a WARN on every course with an overview, which is how readers learn to skim
  past WARNs. Per-segment L3s are still gated.