feat(devkit): simulation runner, CSV export, diurnal load, benchmark

packages/devkit/Cargo.toml

@@ -12,3 +12,8 @@ tokio = { version = "1", features = ["rt-multi-thread", "macros"] }
 
 [dev-dependencies]
 serde_json = "1"
+criterion = { version = "0.5", features = ["html_reports"] }
+
+[[bench]]
+name = "fee_model_bench"
+harness = false

packages/devkit/benches/fee_model_bench.rs

@@ -0,0 +1,15 @@
+use criterion::{criterion_group, criterion_main, Criterion};
+use stellar_devkit::simulation::fee_model::{FeeModel, FeeModelConfig};
+
+fn bench_generate_100k(c: &mut Criterion) {
+    let config = FeeModelConfig {
+        ledger_count: 100_000,
+        ..Default::default()
+    };
+    c.bench_function("fee_model_generate_100k", |b| {
+        b.iter(|| FeeModel::generate(&config))
+    });
+}
+
+criterion_group!(benches, bench_generate_100k);
+criterion_main!(benches);

packages/devkit/src/cli/export.rs

@@ -1,2 +1,21 @@
+use crate::simulation::fee_model::FeePoint;
+use std::fmt::Write as FmtWrite;
+
 /// Exports devkit results to external formats.
 pub struct Export;
+
+impl Export {
+    /// Serialize fee points to CSV string with columns: timestamp,fee,ledger,is_spike.
+    pub fn to_csv(points: &[FeePoint]) -> String {
+        let mut out = String::from("timestamp,fee,ledger,is_spike\n");
+        for p in points {
+            writeln!(out, "{},{},{},{}", p.timestamp, p.fee, p.ledger, p.is_spike).unwrap();
+        }
+        out
+    }
+
+    /// Write fee points to a CSV file.
+    pub fn write_csv(points: &[FeePoint], path: &std::path::Path) -> std::io::Result<()> {
+        std::fs::write(path, Self::to_csv(points))
+    }
+}

packages/devkit/src/harness/scenarios/mod.rs

@@ -27,6 +27,8 @@ impl ScenarioRotator {
     }
 }
 
+use std::path::Path;
+
 /// Loads a scenario JSON file from the given path and returns its contents.
 pub fn load_from_file(path: &Path) -> std::io::Result<String> {
     std::fs::read_to_string(path)