docs: JTS #1094 in-circle FFI scout + corpus code review

[grootstebozewolf]

Summary

• Session 2 (GREEN) of the mesh in-circle lane (topic: mesh, epic Formal proofs for Delaunay triangulation and Voronoi diagram correctness/robustness #68): FFI-backed differential scout of locationtech/jts#1094 (Make isInCircleRobust robust) against Rocq b64_inCircle / nts_rocq_in_circle.
• High-quality corpus code review of the PR (Stage A bound policy, Math.fma, missing Vertex.isCCW, testCircle golden, etc.).
• Product call unchanged: one lane with jts#1212 as tip; #1094 is adaptive-escalation history/reference.

Files

Path	Role
docs/jts-1094-incircle-lane-2026-08.md	Scout outcome + full review
docs/jts-open-prs-scout-2026-08.md	Link session 2 into inventory
oracle/scout_incircle_{ffi.ml,stubs.c,probe.c}	Minimal Phase-5-style in-circle FFI
oracle/gen_jts1094_incircle_scout.py	Generator / gate (Stage A#1094 + FFI + oracle parity)
oracle/jts1094_incircle_vectors.txt	27-vector table
oracle/Makefile	scout-incircle-ffi, jts1094-scout targets
oracle/.gitignore	scout lib/probe build products

Gate (local)

Vectors: 27
FFI pin: POS 1.5
FFI ≡ oracle_bin bit-parity: 0 failures
EXPECTED pin failures: 0
Stage A CERTAIN vs FFI conflicts: 0
Stage A UNCERTAIN: 4 (incl. GEOS955 → FFI POS)
Bound policy diverge (#1094 ≥ vs #1212 >): 6 (vertex permanent=0; same boolean)

Test plan

• Build scout FFI (WSL / Linux):

  make -C oracle scout-incircle-ffi

• Differential gate (exit 0; pin POS 1.5; FFI ≡ oracle_bin bits):

  # Linux: use local oracle_bin after `make -C oracle`
  python3 oracle/gen_jts1094_incircle_scout.py \
    --oracle oracle/oracle_bin \
    --ffi-probe oracle/scout_incircle_probe
  
  # Windows host + WSL oracle binary (as run in session):
  python3 oracle/gen_jts1094_incircle_scout.py \
    --oracle /home/user/nettopologysuite.proofs/oracle/oracle_bin \
    --ffi-probe oracle/scout_incircle_probe

• Or combined Makefile target (needs both oracle_bin and scout probe):

  make -C oracle jts1094-scout

• Optional: full libntsrocq rebuild + wire CI smoke later (not required for merge)