fix: enforce numeric guards in Rhai operator dispatch

crates/fidc-core/src/platform_expr_strategy.rs

@@ -1574,6 +1574,8 @@ impl PlatformExprStrategy {
 
     pub fn new(config: PlatformExprStrategyConfig) -> Self {
         let mut engine = Engine::new();
+        engine.set_fast_operators(false);
+        engine.set_fail_on_invalid_map_property(true);
         // Dynamic scripts cannot carry a nullable boolean through Rhai's
         // logical operators. Reject an unknown comparison instead of letting
         // native NaN comparisons turn missing data into a buy/sell signal.