F.0's row in BEHAVE-EXTRACTOR.md was forward-only — readers landing
on Phase F couldn't tell that F.0 also has a backlog (E.4 held, D.0
subsumption). Add a 'Carry-overs F.0 must unblock' section to the
Phase F prelude and a back-reference on the F.0 checkbox in the
implementation order checklist.