App._post_init now resolves src = paths.get_layouts_dir()/default.ini
and dst = Path.cwd()/manualslop_layout.ini, then calls the drain-plane
helper before the warmup-complete registration block. Errors drain to
self._startup_timeline_errors per the data-oriented convention, so a
missing bundled layout (e.g. partial wheel install) does not crash the
GUI: panels just stay invisible until the user drops a real INI in.
Test fix: test_default_layout_install._GUI_SCRIPT was a relative path,
but the subprocess Popen runs with cwd = temp_workspace where sloppy.py
does not exist. Switched to an absolute path via _PROJECT_ROOT, the
same pattern conftest.py:648 uses for the live_gui fixture.
ed
3d87f8e7ed