refactor(explorer): split explorer into facade and phase modules

artemis/agents/explorer/_facade.py

@@ -0,0 +1,34 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Late-bound access to the ``artemis.agents.explorer.explorer`` facade module.
+
+The Explorer implementation is split across several modules, but external
+callers (and ``unittest.mock.patch`` targets in the test suite) address
+collaborators such as ``settings``, ``StorageManager``, ``draw_dots``,
+``search_ui_func``, ``get_llm`` etc. through the historical module path
+``artemis.agents.explorer.explorer``.  Split-out code therefore resolves those
+names at call time via :func:`facade` instead of importing them directly, so
+patches applied to the facade module keep affecting the split-out code.
+
+The import happens inside the function (not at module top level) to stay safe
+regardless of which module of the package is imported first.
+"""
+
+
+def facade():
+    """Return the ``artemis.agents.explorer.explorer`` module object."""
+    import artemis.agents.explorer.explorer as explorer_module
+
+    return explorer_module