Function fabric_grids_json 

pub fn fabric_grids_json() -> Value

The placed-and-routed tile arrays as JSON — the source of truth for every technical drawing of the fabric, so a drawing of a tile array is the placer’s own output, never hand-drawn. Contains the five config_fabric islands (the 8×3 array that runs 14/14 vectors on both boards) and the Horner cubic residual on both placers (the diagonal route_straight_line behind grid_horner.v, and the area-minimizing route_leveled). Pinned to benchmarks/silicon/fabric_grids.json by fabric_grids_lock.