Release 1.4.2: load-only dialog when nothing is selected

With neither mode derivable (nothing selected, no marker rectangles,
no config) the dialog now opens anyway instead of failing with an
error figure: both radios disabled with their reasons, OK/Save
disabled, Load config… live - a saved config can bootstrap the run.

README: note that macOS/NixOS field tests last ran with plugin v1.3.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HjSRLWQ8ywBBYyakvr3YTx

tests/test_dialog.py

@@ -590,6 +590,55 @@ def test_load_button_cancelled_picker_does_nothing(app, tmp_path,
     assert not dlg.error_label.isVisible()
 
 
+# --- no runnable mode: the load-only dialog ----------------------------------
+
+def _no_mode_dlg(app, load_dir=None, save_callback=None):
+    """Neither mode derivable (nothing selected, no marker rects, no
+    config): main opens the dialog anyway so a config can be loaded."""
+    return _Dialog({}, ORDER, "", "", "", "auto", "auto",
+                   buildup_layers=[], pdn=None, pdn_candidates={},
+                   classic_reason="nothing selected",
+                   pdn_reason="no rectangles found",
+                   save_callback=save_callback, load_dir=load_dir)
+
+
+def test_no_mode_opens_load_only(app, tmp_path):
+    dlg = _no_mode_dlg(app, load_dir=tmp_path,
+                       save_callback=lambda *_a: "x")
+    assert not dlg.mode_classic.isEnabled()
+    assert not dlg.mode_pdn.isEnabled()
+    # no mode is even checked - there is nothing to run
+    assert not dlg.mode_classic.isChecked()
+    assert not dlg.mode_pdn.isChecked()
+    assert not dlg.ok_button.isEnabled()
+    assert not dlg.save_button.isEnabled()
+    assert dlg.load_button.isEnabled()
+    # both reasons and the load hint are shown together
+    text = dlg.reason_label.text()
+    assert "nothing selected" in text
+    assert "no rectangles found" in text
+    assert "Load config…" in text
+
+
+def test_no_mode_load_config_still_works(app, tmp_path, monkeypatch):
+    path = tmp_path / "fill_res_config.saved.json"
+    path.write_text('{"version": 1}', encoding="utf-8")
+    monkeypatch.setattr(dialog_mod, "QFileDialog", _FakePicker)
+    _FakePicker.result = (str(path), "json")
+    dlg = _no_mode_dlg(app, load_dir=tmp_path)
+    dlg._load_config()
+    assert dlg._load_request == path
+    assert dlg.result() == QDialog.Accepted
+
+
+def test_available_modes_keep_ok_and_save_enabled(app, tmp_path):
+    dlg = _dlg(app, pdn=_setup(), save_callback=lambda *_a: "x",
+               load_dir=tmp_path)
+    assert dlg.ok_button.isEnabled()
+    assert dlg.save_button.isEnabled()
+    assert dlg.load_button.isEnabled()
+
+
 # --- save button -------------------------------------------------------------
 
 def _patch_save(monkeypatch, name):