D77 — Coupled-pair work counts every leg check

Decision

A coupled-pair attempt's work is its closed states plus every exact leg check of a start or goal candidate, legal or not; it is added to the router's total every 64 steps, when the work budget and time limit are checked, and leg checks have no per-attempt cap

Alternatives

Count only closed states (old); cap leg checks at the state budget; charge per candidate instead of per check; poll only the time limit

Reason

Rejected candidates were free, so an attempt with every leg blocked by fill polygons ran 635 s at --work 20000 and overran --time 900 by 148 s. Per check follows the cost (0–72 checks per candidate). The cap lost coupling on three of 18 boards at 30 M. Polling the budget keeps budgeted runs deterministic (same output at 1 and 2 threads); the time limit stays a safety stop. Pairs off: byte-identical (quick tier); 17 of 18 pair boards byte-identical at 30 M, the 18th identical once the budget includes its 958,420 leg checks (doc 05 §30)