Critical: review/merge tasks hit an early return in handleTaskCompleted()
that skipped the phase completion check, leaving phases stuck in
in_progress forever. Changed to an if-block wrapping only the merge step.
Also adds requestChangesOnInitiative() which creates/reuses a
"Finalization" phase for initiative-level review feedback, with dedup
guards for both phase and initiative request-changes flows.
65bcbf1a35