fix: retrieve ABACUS autotest outputs

Fixes #1897

Coding-Agent: Codex

Codex-Version: codex-cli 0.149.0

Model: gpt-5.6-sol

Reasoning-Effort: xhigh

Author: njzjz-bot

dpgen/auto_test/ABACUS.py

@@ -252,4 +252,6 @@ def forward_common_files(self, property_type="relaxation"):
         return []
 
     def backward_files(self, property_type="relaxation"):
-        return []
+        # ABACUS stores completion logs, final structures, and parsed results
+        # under this directory for both relaxation and static calculations.
+        return ["OUT.ABACUS"]

tests/auto_test/test_abacus.py

@@ -69,6 +69,9 @@ def test_make_potential_files(self):
         )
         self.assertTrue(os.path.isfile(os.path.join(self.equi_path, "inter.json")))
 
+    def test_backward_files(self):
+        self.assertEqual(self.ABACUS.backward_files(), ["OUT.ABACUS"])
+
     def test_make_input_file_1(self):
         param = self.task_param.copy()
         param["cal_setting"] = {