refactor(test): update test expectations for removed submit route

- Comment out submit route assertions in main_test.go and server_test.go

- Comment out TestTask_OldAPICompatibility in task_test.go

- Update expected route count 31→30 in testenv env_test.go

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

cmd/server/task_test.go

@@ -318,6 +318,8 @@ func TestTask_RetryScenario(t *testing.T) {
 		task.Status, task.RetryCount, task.SlurmJobID)
 }
 
+// [已禁用] 前端已全部迁移到 POST /tasks 接口，旧 API 兼容性测试不再需要。
+/*
 func TestTask_OldAPICompatibility(t *testing.T) {
 	srv, _, cleanup := setupTaskTestServer(t)
 	defer cleanup()
@@ -352,6 +354,7 @@ func TestTask_OldAPICompatibility(t *testing.T) {
 		t.Errorf("expected non-zero job_id, got %v", data["job_id"])
 	}
 }
+*/
 
 func TestTask_ListWithFilters(t *testing.T) {
 	srv, taskStore, cleanup := setupTaskTestServer(t)