refactor(#2077): drop impl-history from broker/dashboard/mcp comments

hive-ag3nt/src/mcp.rs

@@ -535,9 +535,8 @@ fn format_age_secs(secs: u64) -> String {
 }
 
 /// Common envelope around every MCP tool handler: pre-log → run →
-/// post-log. The inbox-status hint used to be appended to every tool
-/// result; that lives in the wake prompt + UI header now, so tool
-/// results stay clean.
+/// post-log. Tool results stay clean — the inbox-status hint lives in
+/// the wake prompt + UI header, not appended here.
 pub async fn run_tool_envelope<F>(tool: &'static str, args: String, body: F) -> String
 where
     F: Future<Output = String>,