Consolidation/true-up after #646-#648. Records the off-serving comprehension
system as one ledger: R1 relational arithmetic, R2 finite-integer constraints,
R3 explicit single-rate + exact minute/hour conversion, the router/contemplation/
proposal loop, the proposal-review reporter, idle_tick read-only visibility, and
the standing router-organ-hygiene invariant. Pins the whole-system lane state
(answer_wrong==0 everywhere) and the off-serving import-disjointness guarantee.
Also fixes a documentation-integrity defect the R2 batch introduced: the R2 ADR
took number 0211, which collided with ADR-0211 (Conformal Falsification Bench,
2026-06-06 — earlier, test-pinned, depended on by ADR-0216). The conformal ADR
keeps 0211; the R2 ADR is renumbered to the next free number 0217. Ratified
decision content unchanged; only the identifier and references move.
generate/constraint_comprehension/solver.py: solve_two_var_linear (order-independent 2x2 integer Cramer's rule over typed constraints), the solve_two_var_count_weight specialization, and solve/answer_constraint_problem driving it from a ConstraintProblem. Four typed refusals: indistinguishable_weights (det==0), non_integer_solution (numer%det!=0, never rounds), negative_solution, verification_failed (identity backstop).
Ties to the C2 gold: solves all 7 solved fixtures to their gold value and refuses all 3 solver_refuses fixtures with EXACTLY the gold-claimed reason (the gold's reason is now solver-verified, not just annotation). Per-refusal meaningful-fail + positive re-substitution. Off-serving. 9 tests.
