feat(obs): integrate dial9-tokio-telemetry for runtime tracing (#2285)

Co-authored-by: heihutu <heihutu@gmail.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

flake.nix

@@ -85,6 +85,7 @@
 
             # Set environment variables for build
             PROTOC = "${pkgs.protobuf}/bin/protoc";
+            RUSTFLAGS = "--cfg tokio_unstable";
 
             doCheck = false;
 
@@ -122,6 +123,7 @@
             ];
 
             PROTOC = "${pkgs.protobuf}/bin/protoc";
+            RUSTFLAGS = "--cfg tokio_unstable";
           };
         }
       );