补 wsClientCore 并发测试 + close() 防 nil conn 守卫

Result: {"status":"keep","total_issues":8,"eslint_errors":0,"eslint_problems":0,"eslint_warnings":0,"golint_canonicalheader":0,"golint_errname":0,"golint_errorlint":1,"golint_exhaustive":0,"golint_forcetypeassert":0,"golint_gosec":0,"golint_intrange":0,"golint_modernize":3,"golint_nilnil":3,"golint_perfsprint":0,"golint_prealloc":0,"golint_recvcheck":1,"golint_test_testifylint":0,"golint_test_thelper":0,"golint_test_total":0,"golint_test_usetesting":0,"golint_total":8,"golint_usestdlibvars":0,"golint_vetx_total":0,"golint_wastedassign":0,"measure_s":77,"tsc_errors":0,"vitest_failed":0,"vitest_total":126}

internal/apps/openflare/websocket/client_core.go

@@ -27,7 +27,9 @@ func (c *wsClientCore) close() {
 	}
 	c.once.Do(func() {
 		close(c.done)
-		_ = c.conn.Close()
+		if c.conn != nil {
+			_ = c.conn.Close()
+		}
 	})
 }