feat: scaffold workspace with bench-common, bench-server, bench-runner

- bench-common: KeyExchangeMode enum, BenchRecord NDJSON struct
- bench-server: CLI stub with --mode and --listen
- bench-runner: CLI stub with --mode, --server, --payload-bytes, --iters, --warmup, --concurrency, --out

Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-members = []
+members = ["bench-common", "bench-runner", "bench-server"]
 resolver = "3"
 
 [workspace.package]
@@ -8,12 +8,16 @@ authors = ["Kristofers Solo <dev@kristofers.xyz>"]
 edition = "2024"
 
 [workspace.dependencies]
+bench-common = { path = "bench-common" }
 claims = "0.8"
 clap = { version = "4.5", features = ["derive"] }
-color-eyre = "0.6"
+miette = { version = "7", features = ["fancy"] }
 rstest = "0.26"
-strum = "0.27"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+strum = { version = "0.27", features = ["derive"] }
 thiserror = "2"
+tokio = { version = "1", features = ["full"] }
 
 [workspace.lints.clippy]
 nursery = "warn"