fix(daytona): migrate legacy-sandbox lookup to cursor-based list() (#24587)

Daytona ships breaking SDK changes on June 10, 2026 — `list()` returns
an iterator and the `page=` offset parameter is removed. We pin
daytona==0.155.0 so we're past the May 24 hard-cutoff, but the
legacy-sandbox resume path in DaytonaEnvironment still passes `page=1`
and reads `.items` off the result.

Switch to `next(iter(results), None)` against a single-result
`list(labels=..., limit=1)` call. Update tests to use `iter([...])`
and drop the `page=1` kwarg from list() assertions.

tests/tools/test_daytona_environment.py

@@ -91,7 +91,7 @@ def make_env(daytona_sdk, monkeypatch):
         if list_return is not None:
             mock_client.list.return_value = list_return
         else:
-            mock_client.list.return_value = SimpleNamespace(items=[])
+            mock_client.list.return_value = iter([])
 
         daytona_sdk.Daytona = MagicMock(return_value=mock_client)
 
@@ -156,13 +156,13 @@ class TestPersistence:
         legacy.process.exec.return_value = _make_exec_response(result="/root")
         env = make_env(
             get_side_effect=daytona_sdk.DaytonaError("not found"),
-            list_return=SimpleNamespace(items=[legacy]),
+            list_return=iter([legacy]),
             persistent=True,
             task_id="mytask",
         )
         legacy.start.assert_called_once()
         env._mock_client.list.assert_called_once_with(
-            labels={"hermes_task_id": "mytask"}, page=1, limit=1)
+            labels={"hermes_task_id": "mytask"}, limit=1)
         env._mock_client.create.assert_not_called()
 
     def test_persistent_creates_new_when_none_found(self, make_env, daytona_sdk):
@@ -176,7 +176,7 @@ class TestPersistence:
         # by checking get() was called with the right sandbox name
         env._mock_client.get.assert_called_with("hermes-mytask")
         env._mock_client.list.assert_called_with(
-            labels={"hermes_task_id": "mytask"}, page=1, limit=1)
+            labels={"hermes_task_id": "mytask"}, limit=1)
 
     def test_non_persistent_skips_lookup(self, make_env):
         env = make_env(persistent=False)