feat: named case-result load combinations with full GUI support

Snapshots the current development tree, headlined by proper load
combinations (user request): a reusable LoadCombination entity of
weighted completed static-case results (e.g. 1.2xDead + 1.6xLive).

- core: LoadCombination/LoadCombinationItem entities, Project
  integration (lookup, unique ids, reference validation)
- services: combinations.py (linear superposition + envelope),
  exported via services __init__
- commands: undoable Add/Delete/Update for combinations
- GUI: Load Combinations manager dialog, Run-dialog evaluation,
  envelope display in Results panel, Combinations tab in Table dock
- tests: unit coverage (validation, math, error paths) + integration
  superposition check vs a single factored run

tests/gui/test_assign_load_pattern_name.py

@@ -0,0 +1,147 @@
+"""AssignLoadDialog lets the user pick or name a load pattern."""
+
+from __future__ import annotations
+
+import pytest
+
+pytest.importorskip("PySide6")
+
+from otko.commands import AddNodalLoadsCommand  # noqa: E402
+from otko.core import (  # noqa: E402
+    LinearTimeSeries,
+    Node,
+    PlainLoadPattern,
+    Project,
+)
+from otko.viewmodels import ProjectViewModel  # noqa: E402
+from otko.views.dialogs.assign_load import AssignLoadDialog  # noqa: E402
+
+
+@pytest.mark.gui
+def test_dialog_defaults_to_new_when_no_patterns(qtbot) -> None:  # type: ignore[no-untyped-def]
+    dlg = AssignLoadDialog(n_selected=1, existing_patterns=[])
+    qtbot.addWidget(dlg)
+    # Only one row, the "<New pattern…>" sentinel.
+    assert dlg._pattern_cb.count() == 1
+    assert dlg.selected_pattern_id() is None
+    assert dlg._new_name_edit.isEnabled()
+
+
+@pytest.mark.gui
+def test_dialog_lists_existing_patterns(qtbot) -> None:  # type: ignore[no-untyped-def]
+    dlg = AssignLoadDialog(
+        n_selected=2,
+        existing_patterns=[(1, "Gravity"), (2, "RefMoment")],
+    )
+    qtbot.addWidget(dlg)
+    # 2 existing + 1 new sentinel.
+    assert dlg._pattern_cb.count() == 3
+    assert dlg._pattern_cb.currentIndex() == 0
+    assert dlg.selected_pattern_id() == 1
+    # Switch to RefMoment.
+    dlg._pattern_cb.setCurrentIndex(1)
+    assert dlg.selected_pattern_id() == 2
+    # The new-name field is disabled for existing picks.
+    assert not dlg._new_name_edit.isEnabled()
+
+
+@pytest.mark.gui
+def test_dialog_enables_name_field_for_new_pattern(qtbot) -> None:  # type: ignore[no-untyped-def]
+    dlg = AssignLoadDialog(
+        n_selected=1,
+        existing_patterns=[(1, "Gravity")],
+    )
+    qtbot.addWidget(dlg)
+    dlg._pattern_cb.setCurrentIndex(1)  # "<New pattern…>"
+    assert dlg.selected_pattern_id() is None
+    assert dlg._new_name_edit.isEnabled()
+    dlg._new_name_edit.setText("RefMoment")
+    assert dlg.new_pattern_name() == "RefMoment"
+
+
+@pytest.mark.gui
+def test_command_creates_named_pattern(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """AddNodalLoadsCommand with new_pattern_name must create a fresh
+    PlainLoadPattern with that name, rather than reusing a default."""
+    vm = ProjectViewModel()
+    vm.new_project(ndm=2, ndf=3)
+    vm.project.nodes.append(Node(id=1, coords=(0, 0, 0)))
+    # Pre-existing 'Gravity' pattern — must NOT be reused when the user
+    # asks for a new one named 'RefMoment'.
+    vm.project.time_series.append(LinearTimeSeries(id=1, name="Gravity"))
+    vm.project.load_patterns.append(
+        PlainLoadPattern(
+            id=1,
+            name="Gravity",
+            time_series_id=1,
+        )
+    )
+
+    vm.apply_command(
+        AddNodalLoadsCommand(
+            vm,
+            {1},
+            (0, 0, 0, 0, 0, 1.0),
+            pattern_id=None,
+            new_pattern_name="RefMoment",
+        )
+    )
+    # Two patterns now: Gravity (id=1) and RefMoment (id=2).
+    names = [p.name for p in vm.project.load_patterns]
+    assert "Gravity" in names and "RefMoment" in names
+    ref = next(p for p in vm.project.load_patterns if p.name == "RefMoment")
+    assert ref.id == 2
+    assert ref.nodal_loads[0].forces[5] == pytest.approx(1.0)
+
+
+@pytest.mark.gui
+def test_command_creates_constant_timeseries_when_requested(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """new_ts_type='Constant' produces a ConstantTimeSeries alongside
+    the new pattern — required for axial preloads in moment-curvature
+    runs where pseudoTime must NOT scale the axial force."""
+    from otko.core import ConstantTimeSeries
+
+    vm = ProjectViewModel()
+    vm.new_project(ndm=2, ndf=3)
+    vm.project.nodes.append(Node(id=1, coords=(0, 0, 0)))
+    vm.apply_command(
+        AddNodalLoadsCommand(
+            vm,
+            {1},
+            (-180, 0, 0, 0, 0, 0),
+            pattern_id=None,
+            new_pattern_name="AxialP",
+            new_ts_type="Constant",
+        )
+    )
+    # Pattern + TimeSeries both created with the "AxialP" name.
+    assert vm.project.load_patterns[0].name == "AxialP"
+    ts = vm.project.time_series[0]
+    assert isinstance(ts, ConstantTimeSeries)
+    assert ts.name == "AxialP"
+
+
+@pytest.mark.gui
+def test_command_reuses_existing_pattern_by_id(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """pattern_id=1 reuses the existing pattern — doesn't create new."""
+    vm = ProjectViewModel()
+    vm.new_project(ndm=2, ndf=3)
+    vm.project.nodes.append(Node(id=1, coords=(0, 0, 0)))
+    vm.project.time_series.append(LinearTimeSeries(id=1, name="Existing"))
+    vm.project.load_patterns.append(
+        PlainLoadPattern(
+            id=1,
+            name="Existing",
+            time_series_id=1,
+        )
+    )
+    vm.apply_command(
+        AddNodalLoadsCommand(
+            vm,
+            {1},
+            (0, 0, 0, 0, 0, 5.0),
+            pattern_id=1,
+        )
+    )
+    assert len(vm.project.load_patterns) == 1
+    assert len(vm.project.load_patterns[0].nodal_loads) == 1