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_material_form_ranges.py

@@ -0,0 +1,155 @@
+"""Material form spin-box ranges must accept any consistent unit system.
+
+Regression: the old Concrete01 form capped ``fpc`` at -1e3 (Pa),
+silently clamping kip-in / ksi users' ``-6`` input to ``-1000``.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+pytest.importorskip("PySide6")
+
+from otko.views.dialogs.material_forms import (  # noqa: E402
+    Concrete01Form,
+    Concrete02Form,
+    Steel01Form,
+    Steel02Form,
+)
+
+
+@pytest.mark.gui
+def test_concrete01_accepts_ksi_values(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """User types -6 (ksi) → spinbox stores -6, not clamped to -1000."""
+    form = Concrete01Form()
+    qtbot.addWidget(form)
+    form._fpc.setValue(-6.0)
+    form._epsc0.setValue(-0.004)
+    form._fpcu.setValue(-5.0)
+    form._epsU.setValue(-0.014)
+
+    assert form._fpc.value() == pytest.approx(-6.0)
+    assert form._epsc0.value() == pytest.approx(-0.004)
+    assert form._fpcu.value() == pytest.approx(-5.0)
+    assert form._epsU.value() == pytest.approx(-0.014)
+
+
+@pytest.mark.gui
+def test_concrete01_still_accepts_si_pa_values(qtbot) -> None:  # type: ignore[no-untyped-def]
+    form = Concrete01Form()
+    qtbot.addWidget(form)
+    form._fpc.setValue(-30e6)
+    form._fpcu.setValue(-5e6)
+    assert form._fpc.value() == pytest.approx(-30e6)
+    assert form._fpcu.value() == pytest.approx(-5e6)
+
+
+@pytest.mark.gui
+def test_concrete02_accepts_ksi_values(qtbot) -> None:  # type: ignore[no-untyped-def]
+    form = Concrete02Form()
+    qtbot.addWidget(form)
+    form._fpc.setValue(-6.0)
+    form._fpcu.setValue(-5.0)
+    form._ft.setValue(0.6)  # ksi tensile strength
+    assert form._fpc.value() == pytest.approx(-6.0)
+    assert form._fpcu.value() == pytest.approx(-5.0)
+    assert form._ft.value() == pytest.approx(0.6)
+
+
+@pytest.mark.gui
+def test_steel01_accepts_ksi_values(qtbot) -> None:  # type: ignore[no-untyped-def]
+    form = Steel01Form()
+    qtbot.addWidget(form)
+    form._fy.setValue(60.0)  # ksi
+    form._e0.setValue(30000.0)  # ksi
+    form._b.setValue(0.01)
+    assert form._fy.value() == pytest.approx(60.0)
+    assert form._e0.value() == pytest.approx(30000.0)
+
+
+@pytest.mark.gui
+def test_steel02_accepts_ksi_values(qtbot) -> None:  # type: ignore[no-untyped-def]
+    form = Steel02Form()
+    qtbot.addWidget(form)
+    form._fy.setValue(60.0)
+    form._e0.setValue(30000.0)
+    assert form._fy.value() == pytest.approx(60.0)
+    assert form._e0.value() == pytest.approx(30000.0)
+
+
+@pytest.mark.gui
+def test_spinbox_uses_c_locale_for_decimal_separator(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """Spinboxes must force '.' as the decimal separator regardless of
+    the OS locale. On tr_TR / de_DE Windows the default QLocale expects
+    ',' and silently rejects Tcl-style '-0.004' inputs."""
+    from PySide6.QtCore import QLocale
+
+    form = Concrete01Form()
+    qtbot.addWidget(form)
+    assert form._epsc0.locale().decimalPoint() == "."
+    assert form._fpc.locale().decimalPoint() == "."
+    # Even if we fake a Turkish default locale, the spinbox's own
+    # locale stays C.
+    QLocale.setDefault(QLocale(QLocale.Language.Turkish))
+    try:
+        form2 = Concrete01Form()
+        qtbot.addWidget(form2)
+        assert form2._epsc0.locale().decimalPoint() == "."
+    finally:
+        QLocale.setDefault(QLocale(QLocale.Language.C))
+
+
+@pytest.mark.gui
+def test_concrete01_epsc0_accepts_four_thousandths(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """Regression: the user's -0.004 must stick exactly after setValue."""
+    form = Concrete01Form()
+    qtbot.addWidget(form)
+    form._epsc0.setValue(-0.004)
+    assert form._epsc0.value() == pytest.approx(-0.004, abs=1e-12)
+    form._epsU.setValue(-0.014)
+    assert form._epsU.value() == pytest.approx(-0.014, abs=1e-12)
+
+
+@pytest.mark.gui
+def test_spinbox_keyboard_tracking_is_off(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """With keyboardTracking=False, typing '-0.004' character-by-character
+    doesn't clamp intermediate values to the range. The final commit
+    happens on Enter / focus-out, preserving the user's input."""
+    form = Concrete01Form()
+    qtbot.addWidget(form)
+    assert not form._epsc0.keyboardTracking()
+    assert not form._fpc.keyboardTracking()
+
+
+@pytest.mark.gui
+def test_concrete01_strain_range_allows_zero_max(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """The spin-box max for strain fields is 0 (Pydantic rejects 0
+    at commit time); any intermediate typing value stays in range."""
+    form = Concrete01Form()
+    qtbot.addWidget(form)
+    assert form._epsc0.maximum() == pytest.approx(0.0)
+    assert form._epsU.maximum() == pytest.approx(0.0)
+
+
+@pytest.mark.gui
+def test_concrete01_round_trip_preserves_ksi_values(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """Form → Concrete01 model → form round-trip keeps ksi values intact."""
+    form = Concrete01Form()
+    qtbot.addWidget(form)
+    form._fpc.setValue(-6.0)
+    form._epsc0.setValue(-0.004)
+    form._fpcu.setValue(-5.0)
+    form._epsU.setValue(-0.014)
+    form._name_edit.setText("Core-Conc")
+    form._material_id = 1
+    mat = form.read()
+    assert mat.fpc == pytest.approx(-6.0)
+    assert mat.epsc0 == pytest.approx(-0.004)
+    assert mat.fpcu == pytest.approx(-5.0)
+    assert mat.epsU == pytest.approx(-0.014)
+    # Round-trip through a fresh form.
+    form2 = Concrete01Form()
+    qtbot.addWidget(form2)
+    form2.populate(mat)
+    assert form2._fpc.value() == pytest.approx(-6.0)
+    assert form2._fpcu.value() == pytest.approx(-5.0)