Fix hyper_cleaning 2D prohibition double-triggering for 1D cases

In 1D simulations n==0 and p==0, so both the 1D and 2D prohibition
checks were firing simultaneously. Gate the 2D check on n > 0 so
it only triggers for configurations that are actually 2D.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sbryngelson

toolchain/mfc/case_validator.py

@@ -1042,7 +1042,7 @@ def check_mhd_simulation(self):
                      "Hyperbolic cleaning requires mhd to be enabled")
         self.prohibit(hyper_cleaning and n is not None and n == 0,
                      "Hyperbolic cleaning is not supported for 1D simulations")
-        self.prohibit(hyper_cleaning and p is not None and p == 0,
+        self.prohibit(hyper_cleaning and n is not None and n > 0 and p is not None and p == 0,
                      "Hyperbolic cleaning is not supported for 2D simulations")