Fix DebugServerTests issue

Author: Kyle-Ye

Tests/OpenGraphCompatibilityTests/Debug/DebugServerTests.swift

@@ -7,6 +7,7 @@ import CoreFoundation
 import Foundation
 import Testing
 
+@MainActor
 struct DebugServerTests {
     @Test
     func testMode0() {
@@ -22,11 +23,12 @@ struct DebugServerTests {
         .disabled(if: compatibilityTestEnabled, "Skip on AG due to internal_diagnostics check"),
     )
     func testMode1() throws {
-        _ = try #require(OGDebugServer.start(mode: 1))
+        let _ = try #require(OGDebugServer.start(mode: 1))
         let url = try #require(OGDebugServer.copyURL())
         let urlString = (url as URL).absoluteString
         #expect(urlString.hasPrefix("graph://"))
         OGDebugServer.run(timeout: 1)
+        OGDebugServer.stop()
     }
 }
 #endif