feat: connect portfolio loss to finalized accounting and daily risk clock

crates/fidc-core/src/portfolio_loss.rs

@@ -453,8 +453,10 @@ mod tests {
             state.decide(date(2), Some(date(1)), time(2, 1), 0.9),
             Err(PortfolioLossError::SessionDiscontinuity)
         );
-        let mut late = state.clone();
-        late.last_session.as_mut().unwrap().available_at = time(2, 1);
+        let mut late = PortfolioLossState::new(config(), date(0)).unwrap();
+        let mut delayed = session(0, 1.0, 0.99, 1.0);
+        delayed.available_at = time(2, 1);
+        late.observe(delayed).unwrap();
         assert_eq!(
             late.decide(date(1), Some(date(0)), time(1, 1), 0.9),
             Err(PortfolioLossError::ObservationNotVisible)
@@ -481,4 +483,35 @@ mod tests {
         assert_eq!(decision.target_exposure, 0.9);
         assert_eq!(state.last_session().unwrap().date, date(19));
     }
+
+    #[test]
+    fn restored_state_rejects_changed_policy_and_forged_cooldown() {
+        let state = PortfolioLossState::new(config(), date(0)).unwrap();
+        let mut changed = config();
+        changed.floor_exposure = 0.5;
+        assert_eq!(
+            state.validate(&changed),
+            Err(PortfolioLossError::StateMismatch)
+        );
+        let mut forged = state.clone();
+        forged.cooldown_remaining = 1;
+        assert_eq!(
+            forged.validate(&config()),
+            Err(PortfolioLossError::StateMismatch)
+        );
+    }
+
+    #[test]
+    fn nav_serialization_preserves_float_bits() {
+        let mut seed = 0xabcddcba12345678_u64;
+        for _ in 0..2000 {
+            seed ^= seed << 13;
+            seed ^= seed >> 7;
+            seed ^= seed << 17;
+            let value = 0.01 + (seed as f64 / u64::MAX as f64) * 9.99;
+            let serialized = serde_json::to_string(&value).unwrap();
+            let restored: f64 = serde_json::from_str(&serialized).unwrap();
+            assert_eq!(value.to_bits(), restored.to_bits());
+        }
+    }
 }