nx_research_investigate.nx

nx_research_investigate.nx -- S4: the INVESTIGATION LOOP over the S1-S3 research cycle (recursive self-growth, $0). DISTINCT from nx_research_loop.nx (the 2026-06-17 physics/energy/frontier autonomous driver). This one drives the grounding cycle: synthesize (S1) -> verify (S2) -> ground-check (S3) -> if grounding GAPS remain, investigate again -- and decides HONESTLY when to stop: GROUNDED (0 gaps) / BUDGET (iteration cap) / STALLED (gaps stopped decreasing, so it never loops forever). gaps = uncited + unverified + unanswered sub-questions. The control is deterministic/$0; the per-iteration synthesis composes S1-S3 (model-gated). This is the "propose -> gate -> measure -> bank -> next" loop we run by hand every session, made an organ. license_tier: ORIGINAL