candidate_03 — Localization index (Q1 instrument)

Assigned by Phase 4 (research/candidate_ranking.md). Core gaps: G17 (+G11/G12 as measurement layers).

First falsifier: the index must read ≈1 on Tracr-compiled circuits and ≈0 on random-init models; otherwise it is broken before touching real models.

Status: assigned — prototyping starts after the mandatory substrate (expH capture-cost frontier, expA/expD noise floors, map-cards v0). Hypothesis will be registered in hypothesis.md before any run (charter §10).