fix(env): default INCLUDE_SOURCES to empty string (#223)

* fix(env): default INCLUDE_SOURCES to empty string

* test(env): patch resolved config path in include sources test

tests/test_env_include_sources_default.py

@@ -0,0 +1,14 @@
+from scripts.lib import env
+
+
+def test_include_sources_defaults_to_empty_string(monkeypatch, tmp_path):
+    # Ensure the env var is not set
+    monkeypatch.delenv("INCLUDE_SOURCES", raising=False)
+
+    # Avoid reading any real user config file by patching the resolved module path directly
+    monkeypatch.setattr(env, "CONFIG_FILE", tmp_path / "does-not-exist.env")
+
+    cfg = env.get_config()
+
+    assert "INCLUDE_SOURCES" in cfg
+    assert cfg["INCLUDE_SOURCES"] == ""