fix(tests): update mocks for file sync changes

- Modal snapshot tests: accept **kw in iter_skills_files/iter_cache_files
  mock lambdas to match new container_base kwarg
- SSH preflight test: mock _detect_remote_home, _ensure_remote_dirs,
  init_session, and FileSyncManager added in file sync PR

tests/tools/test_modal_snapshot_isolation.py

@@ -124,8 +124,8 @@ def _install_modal_test_modules(
     sys.modules["tools.interrupt"] = types.SimpleNamespace(is_interrupted=lambda: False)
     sys.modules["tools.credential_files"] = types.SimpleNamespace(
         get_credential_file_mounts=lambda: [],
-        iter_skills_files=lambda: [],
-        iter_cache_files=lambda: [],
+        iter_skills_files=lambda **kw: [],
+        iter_cache_files=lambda **kw: [],
     )
 
     from_id_calls: list[str] = []