nx_param_tune.nx

nx_param_tune.nx -- X-PRM-003 rung1: autonomous single-variable param tuning (RSI). Picks ONE TUNABLE param (triage_drill_cap, the documented first target), reads its CURRENT value from params.tsv, MEASURES its named effect meter over REAL data (the failure-evidence DEMAND = count of RED rows the cap must cover), does a seed-fixed sweep over [2,8], and PROPOSES a new value (gate-judged, NOT auto-applied -- written to param_proposals.tsv). Honest no-overclaim: the meter here is failure-coverage (real); fuller factors (Doctor route-time, token-cost model) = rung2. CONSERVATIVE: a QUIET signal (demand=0) proposes HOLD -- never tune a cap down on a momentary lull. Self-validating: synthetic controls prove the proposal RESPONDS to the measured demand (no false-green).