fix(HEL-461): 后台整组切换异常统一为 FAILED_PRECONDITION

管理后台补数在切换事务中断时不再抛出原始异常，
统一映射为 ApiError FAILED_PRECONDITION，并保留旧完整版本。

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: multica-agent <github@multica.ai>

xiaobai-datahub/tests/test_atomic_release.py

@@ -367,6 +367,29 @@ class ForceBoundaryEntryTests(unittest.TestCase):
         with self.assertRaises(ApiError):
             admin.backfill("daily", TRADE_DATE, "wrong", f"daily:{TRADE_DATE}", "tester")
 
+    def test_admin_backfill_switch_crash_is_failed_precondition(self) -> None:
+        from datahub.admin_api import AdminAPI
+        from datahub.auth import AuthService
+        from datahub.crypto import SecretVault
+        from datahub.scheduler import Scheduler
+        from datahub.serving import ApiError
+
+        vault = SecretVault(self.pipe.settings.encryption_key)
+        auth = AuthService(self.db, vault, self.pipe.settings.api_token, "StartPass1")
+        admin = AdminAPI(self.db, self.pipe, Scheduler(self.db, self.pipe), auth)
+        before = publications_map(self.db, TRADE_DATE)
+
+        def explode() -> None:
+            raise RuntimeError("killed mid-switch")
+
+        self.pipe.before_commit = explode
+        with self.assertRaises(ApiError) as ctx:
+            admin.backfill("valuation", TRADE_DATE, "StartPass1", f"valuation:{TRADE_DATE}", "tester")
+        self.assertEqual(ctx.exception.code, "FAILED_PRECONDITION")
+        self.assertIn("killed mid-switch", ctx.exception.message)
+        # previous complete A/B versions keep serving
+        self.assertEqual(publications_map(self.db, TRADE_DATE), before)
+
 
 if __name__ == "__main__":
     unittest.main()