docs: drop stale two-loop/two-binary framings (single hive serve loop)

hive-ag3nt/src/serve_common.rs

@@ -50,9 +50,9 @@ pub struct TurnRowArgs<'a> {
     pub open_reminders_count: Option<u64>,
 }
 
-/// Assemble a `TurnStatRow` from the harness's per-turn state. Used by both
-/// the agent and manager serve loops — the shape is identical, only the
-/// post-turn count fetch helpers differ (and those stay in each binary).
+/// Assemble a `TurnStatRow` from the harness's per-turn state. Lives here
+/// (rather than inline in the `hive` serve loop) so it stays wire-type-free
+/// and unit-testable; the binary just feeds it the post-turn counts.
 #[must_use]
 pub fn build_row(args: TurnRowArgs<'_>) -> TurnStatRow {
     let TurnRowArgs {