core/comprehension_attempt/router.py: route_setup tries R1 then R2, collects both attempts, and selects a setup ONLY when exactly one organ admits one. Zero->all_refused; >=2 with differing signatures->ambiguous (refuse, never pick); cross-organ signatures never coincide so two admitting organs always resolve to ambiguous. No scoring, no solving.
wrong=0 invariant asserted: every routed R2 setup is byte-equal to the independent gold signature. Each gold problem routes to exactly its owning organ (R2 well-formed->r2; R1 admitted->r1; refused->all_refused); none is ambiguous. 4 router tests.
