- Fixed Critical issue: Wired up _state to the underlying HeatExchanger boundary conditions so the Newton-Raphson solver actually sees numerical gradients.
- Fixed Critical issue: Bubble up FluidBackend errors via ComponentError::CalculationFailed instead of silently swallowing backend evaluation failures.
- Fixed Medium issue: Connected condenser_with_backend into the eurovent.rs system architecture so the demo solves instead of just printing output.
- Fixed Medium issue: Removed heavy FluidId clones inside query loop.
- Fixed Low issue: Added physical validations to HxSideConditions.
