nx_handoff_gate.nx

nx_handoff_gate.nx -- SHARED deep-gate primitives (the DRY keystone of the sensor-gap program). Per [[feedback-handoff-chain-sota-gate-doctrine]] step 1: makes deepening ANY gate cheap (rule 15 DRY) instead of hand-rolling ~3000 liar-killers. Three sensor families, one import: LIAR-KILLERS -- hg_neg_control (a wrong-input score must stay under a floor, else the metric is GAMED/broken), hg_monotonic_* (physics: drift accumulates, counts don't jump back), hg_invariant_le/ge (bounds: drifted can never beat its clean floor), hg_evidence_file (a claim's artifact must OPEN on disk -- never asserted). REGRESSION -- hg_baseline_load (absent baseline => -1, NEVER fabricated) + hg_no_backslide / hg_no_worsen (stored SOTA-track guard: a change that worsens any tracked value = RED) + hg_baseline_print (the canonical capture line). TELEMETRY -- HgStage per-handoff records (quality/bytes/time/fail) + hg_chain_report (per-stage table, not just a final number) + LOCALIZERS hg_chain_worst_drop (WHICH handoff lost the most quality) and hg_chain_max_time (WHERE the time goes). Pure logic + read-only I/O; deterministic; no writes (never-brick by construction). Library (no main); proven by runtime/_hdl_build/nx_handoff_gate_proof.nx. First consumer: nx_sensor_gap_census. license_tier: ORIGINAL