Document tokio exact pin in integration-tests Cargo.toml

Adds inline comment so future maintainers know why the version is pinned
with `=` rather than a range constraint.

Author: prk-Jr

crates/integration-tests/Cargo.toml

@@ -30,7 +30,7 @@ edgezero-adapter-axum = { git = "https://github.com/stackpop/edgezero", rev = "3
 edgezero-core = { git = "https://github.com/stackpop/edgezero", rev = "38198f9839b70aef03ab971ae5876982773fc2a1" }
 axum = "0.8.9"
 tower = { version = "0.4", features = ["util"] }
-tokio = { version = "=1.52.3", features = ["rt-multi-thread", "macros"] }
+tokio = { version = "=1.52.3", features = ["rt-multi-thread", "macros"] } # exact pin — keep in sync with workspace-resolved tokio version
 http = "1"
 http-body-util = "0.1"
 bytes = "1"