test: multi-target detours around staggered water barriers

Beads: trasser-staggered-obstacles. Depends on !68 (merged). Two new module tests: independently specified feasible polylines and proof that every straight attachment is blocked; solve across 6 rotated/reordered configurations, typed IDs, water avoidance, budget accounting and CurrentResultVerifier. No production changes: no reproduced routing defect. Local clean Java 4/4 PASS including courtyard regressions; docs1135/1135; catalogue227 valid; diff-check PASS. Not hidden-set/HTTP/stand acceptance or benchmark. No auto-merge requested. Prepared with Codex.