Fail the aggregate checker's remaining checks on a NaN response #2759

The aggregate checker passes a NaN response on four checks: own-head, declared-reader containment, spending rises and the model total. Each one compares the response with a threshold, and any comparison with NaN returns false. #2758 closes this gap for undeclared tax movement and leaves these four alone.

Finite baselines can reach it. With tax_b at £5 and tax_a = sqrt(5 - tax_b), the checker raises tax_b by £1 and tax_a turns NaN. If tax_a declares its read of tax_b, counted_once reports pass with a NaN coefficient, on main and on #2758. We haven't found a current-law UK formula that does this.

Two undeclared heads that both turn NaN give a different result. Main reports pass, and #2758 stops when it sets the held heads as inputs:

ValueError: Unable to set value for variable "tax_c", as the input contains NaN values.

The checker should:

• fail a non-finite response on all four checks, with a property test for +inf, -inf and NaN on each;
• report two NaN heads as a failed check that names them, and carry on to the next component.

🤖 Generated with Claude Code