fix(tests): patch _get_session_service directly to eliminate parallel-worker race condition

The root cause was a race condition in parallel Behave workers caused by
mutating a module-level singleton (_service) in
cleveragents.cli.commands.session. Concurrent cleanup in one worker could
reset _service to None while another worker was still using it, leading to
intermittent tell command test failures and exit code 1.

The fix patches the _get_session_service function directly in the affected
test steps (session_cli_coverage_boost_steps.py and
session_cli_uncovered_branches_steps.py) to avoid mutating the module-level
_service, and adds a reset call in features/environment.py's after_scenario
to ensure the singleton is cleared between scenarios, preventing stale
service instances from leaking across tests.

Closes #9121

features/environment.py

@@ -713,6 +713,19 @@ def after_scenario(context, scenario):
     except ImportError:
         pass
 
+    # Reset session CLI module-level service singleton so that no stale
+    # service instance leaks into the next scenario.  Without this reset,
+    # a scenario that sets _service to a real container-constructed instance
+    # would leave it cached; a subsequent scenario that patches _service
+    # via unittest.mock.patch would restore to the stale real instance on
+    # cleanup, causing the next scenario to hit the real container and fail.
+    try:
+        from cleveragents.cli.commands.session import _reset_session_service
+
+        _reset_session_service()
+    except ImportError:
+        pass
+
     # Clean up service instances
     for attr in ["context_service", "plan_service", "project_service"]:
         if hasattr(context, attr):

features/steps/session_cli_coverage_boost_steps.py

@@ -101,7 +101,20 @@ def _mock_service() -> MagicMock:
 
 
 def _patch_service(context, svc):
-    patcher = patch("cleveragents.cli.commands.session._service", svc)
+    """Patch _get_session_service to return *svc* deterministically.
+
+    Patching the function directly (rather than the module-level ``_service``
+    attribute) prevents a race condition in parallel Behave workers: if a
+    concurrent worker's cleanup resets ``_service`` to ``None`` while this
+    scenario's CLI command is executing, ``_get_session_service()`` would fall
+    through to the real DI container and raise, producing a spurious exit
+    code 1.  Patching the function itself short-circuits the cache check
+    entirely and is immune to cross-worker ``_service`` mutations.
+    """
+    patcher = patch(
+        "cleveragents.cli.commands.session._get_session_service",
+        return_value=svc,
+    )
     patcher.start()
     context._scvbst_cleanups.append(patcher.stop)
 

features/steps/session_cli_uncovered_branches_steps.py

@@ -72,12 +72,24 @@ def _mock_service() -> MagicMock:
     return svc
 
 
-# ---- helpers to patch the module-level _service ---------------------------
+# ---- helpers to patch the module-level service accessor -------------------
 
 
 def _patch_service(context, svc):
-    """Patch session._service and register cleanup."""
-    patcher = patch("cleveragents.cli.commands.session._service", svc)
+    """Patch _get_session_service to return *svc* deterministically.
+
+    Patching the function directly (rather than the module-level ``_service``
+    attribute) prevents a race condition in parallel Behave workers: if a
+    concurrent worker's cleanup resets ``_service`` to ``None`` while this
+    scenario's CLI command is executing, ``_get_session_service()`` would fall
+    through to the real DI container and raise, producing a spurious exit
+    code 1.  Patching the function itself short-circuits the cache check
+    entirely and is immune to cross-worker ``_service`` mutations.
+    """
+    patcher = patch(
+        "cleveragents.cli.commands.session._get_session_service",
+        return_value=svc,
+    )
     patcher.start()
     context._cleanup_handlers.append(patcher.stop)