chore(#1474): add reason= to remaining bare clippy allows outside dashboard

hive-matrix-mcp/src/bin/mcp.rs

@@ -147,7 +147,11 @@ struct InviteUserArgs {
 }
 
 struct MatrixBridge {
-    #[allow(dead_code)]
+    #[allow(
+        dead_code,
+        reason = "populated by the #[tool_router] macro; the generated \
+                  ServerHandler wiring consumes it, the field is never read directly"
+    )]
     tool_router: rmcp::handler::server::router::tool::ToolRouter<Self>,
 }