fix: separate historical session capacity audits from execution sizing

crates/fidc-core/src/engine.rs

@@ -122,6 +122,7 @@ impl DailyEquityPoint {
 
 #[derive(Debug, Clone)]
 pub struct BacktestResult {
+    pub capacity_audit: crate::execution_capacity::CapacityAuditSummary,
     pub strategy_name: String,
     pub equity_curve: Vec<DailyEquityPoint>,
     pub benchmark_series: Vec<BenchmarkSnapshot>,
@@ -280,6 +281,7 @@ pub struct AnalyzerRiskSummary {
 
 #[derive(Debug, Clone, Serialize)]
 pub struct AnalyzerReport {
+    pub capacity_audit: crate::execution_capacity::CapacityAuditSummary,
     pub strategy_name: String,
     pub trades: Vec<AnalyzerTradeRow>,
     pub positions: Vec<AnalyzerPositionRow>,
@@ -294,6 +296,7 @@ pub struct AnalyzerReport {
 impl BacktestResult {
     pub fn analyzer_report(&self) -> AnalyzerReport {
         AnalyzerReport {
+            capacity_audit: self.capacity_audit.clone(),
             strategy_name: self.strategy_name.clone(),
             trades: self
                 .fills
@@ -2102,6 +2105,7 @@ where
             .map(|(execution_date, _)| *execution_date)
             .collect::<Vec<_>>();
         let mut result = BacktestResult {
+            capacity_audit: self.broker.capacity_audit_summary(),
             strategy_name: self.strategy.name().to_string(),
             benchmark_series: self
                 .data
@@ -3415,6 +3419,16 @@ where
                 execution_date,
             );
             let daily_fill_count = result.fills.len() - day_fill_start;
+            for audit in self.broker.audit_completed_session_capacity(execution_date, &self.data)? {
+                result.capacity_audit.observe(&audit);
+                // Keep every audit in the durable event store, independent of
+                // debug phase retention. It never changes earlier executions.
+                result.process_events.push(ProcessEvent {
+                    date: execution_date, kind: ProcessEventKind::SessionCapacityAudit,
+                    order_id: None, symbol: Some(audit.symbol.clone()), side: None,
+                    detail: serde_json::to_string(&audit).map_err(|error| BacktestError::Execution(error.to_string()))?,
+                });
+            }
             let daily_order_count = result.order_events.len() - day_order_start;
             let execution_risk_decisions =
                 risk_decisions_from_order_events(&result.order_events[day_order_start..]);