feat(components): add ThermoState generators and Eurovent backend demo

crates/fluids/benches/cache_10k.rs

@@ -0,0 +1,54 @@
+//! Benchmark: 10k repeated (P,T) queries — cached vs uncached (Story 2.4 AC#4).
+//!
+//! Compares throughput of CachedBackend vs raw backend for repeated same-state queries.
+//! Cached path should show significant speedup when the backend is expensive (e.g. CoolProp).
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use entropyk_fluids::{
+    CachedBackend, FluidBackend, FluidId, Property, ThermoState, TestBackend,
+};
+use entropyk_core::{Pressure, Temperature};
+
+const N_QUERIES: u32 = 10_000;
+
+fn bench_uncached_10k(c: &mut Criterion) {
+    let backend = TestBackend::new();
+    let state = ThermoState::from_pt(
+        Pressure::from_bar(1.0),
+        Temperature::from_celsius(25.0),
+    );
+    let fluid = FluidId::new("R134a");
+
+    c.bench_function("uncached_10k_same_state", |b| {
+        b.iter(|| {
+            for _ in 0..N_QUERIES {
+                black_box(
+                    backend.property(fluid.clone(), Property::Density, state.clone()).unwrap(),
+                );
+            }
+        });
+    });
+}
+
+fn bench_cached_10k(c: &mut Criterion) {
+    let inner = TestBackend::new();
+    let cached = CachedBackend::new(inner);
+    let state = ThermoState::from_pt(
+        Pressure::from_bar(1.0),
+        Temperature::from_celsius(25.0),
+    );
+    let fluid = FluidId::new("R134a");
+
+    c.bench_function("cached_10k_same_state", |b| {
+        b.iter(|| {
+            for _ in 0..N_QUERIES {
+                black_box(
+                    cached.property(fluid.clone(), Property::Density, state.clone()).unwrap(),
+                );
+            }
+        });
+    });
+}
+
+criterion_group!(benches, bench_uncached_10k, bench_cached_10k);
+criterion_main!(benches);