Added document-frequency (IDF-style) weighting -- each shared word contributes 1/docfreq instead of a flat 1 -- plus a 1.0 minimum weighted-score threshold and a near-tie check on weighted score. Catches a 3rd false-positive class round 1 missed: a lone generic-word match with no tie to catch it (T00-DESCFIELD repro, matched on api+stale alone). Threshold calibrated against 10 real backlog task strings from this session.