fix: ElasticSectionForm round-trips the SectionShape union

The form still passed flat b/h/d/tw/tf/diameter fields, which
ElasticSection (extra='forbid') rejects, so reading any elastic
section crashed. Rebuild the display-only hint as a PipeShape /
AngleShape / RectShape member instead; an incomplete shape degrades
to None rather than raising.

src/otko/views/dialogs/section_forms.py

@@ -19,8 +19,11 @@ from PySide6.QtWidgets import (
 )
 
 from otko.core import (
+    AngleShape,
     ElasticSection,
     FiberSection,
+    PipeShape,
+    RectShape,
     SectionAggregator,
 )
 
@@ -94,14 +97,13 @@ class SectionFormBase(QWidget):
 class ElasticSectionForm(SectionFormBase):
     type_label = "Elastic Section"
 
-    #: Shape → visible display-only dimensions. ``None`` hides them all.
+    #: Shape kind → visible display-only dimensions (see the core
+    #: ``SectionShape`` union). ``None`` hides them all.
     _SHAPE_DIMS: ClassVar[dict[str | None, tuple[str, ...]]] = {
         None: (),
-        "rect": ("b", "h"),
-        "I": ("b", "d", "tw", "tf"),
-        "H": ("b", "d", "tw", "tf"),
-        "pipe": ("diameter",),
-        "circle": ("diameter",),
+        "rect": ("b", "d"),
+        "angle": ("b", "d", "t"),
+        "pipe": ("od", "t"),
     }
 
     def __init__(self, parent: QWidget | None = None) -> None:
@@ -127,14 +129,14 @@ class ElasticSectionForm(SectionFormBase):
         self._layout.addRow(QLabel("<i>Extruded-view shape (display only).</i>"))
         self._shape = QComboBox()
         self._shape.addItem("(none)", None)
-        for key in ("rect", "I", "H", "pipe", "circle"):
+        for key in ("rect", "angle", "pipe"):
             self._shape.addItem(key, key)
         self._shape.currentIndexChanged.connect(self._update_dim_visibility)
         self._layout.addRow("Shape:", self._shape)
 
         self._dim_spins: dict[str, QDoubleSpinBox] = {}
         self._dim_labels: dict[str, QLabel] = {}
-        for key in ("b", "h", "d", "tw", "tf", "diameter"):
+        for key in ("b", "d", "t", "od"):
             spin = _opt_spin()
             lbl = QLabel(f"{key}:")
             self._dim_spins[key] = spin
@@ -160,20 +162,15 @@ class ElasticSectionForm(SectionFormBase):
             self._g.setValue(s.G)
         if s.J is not None:
             self._j.setValue(s.J)
-        idx = self._shape.findData(s.shape)
+        kind = getattr(s.shape, "kind", None) if s.shape is not None else None
+        idx = self._shape.findData(kind)
         self._shape.setCurrentIndex(idx if idx >= 0 else 0)
         for key, spin in self._dim_spins.items():
-            v = getattr(s, key, None)
+            v = getattr(s.shape, key, None) if s.shape is not None else None
             spin.setValue(v if v is not None else _UNSET_SENTINEL)
         self._update_dim_visibility()
 
     def _read_specific(self, sid: int) -> ElasticSection:
-        shape = self._shape.currentData()
-        visible = set(self._SHAPE_DIMS.get(shape, ()))
-        dims = {
-            key: (_opt_value(spin) if key in visible else None)
-            for key, spin in self._dim_spins.items()
-        }
         return ElasticSection(
             id=sid,
             name=self._name_edit.text(),
@@ -183,10 +180,38 @@ class ElasticSectionForm(SectionFormBase):
             Iy=self._iy.value(),
             G=self._g.value(),
             J=self._j.value(),
-            shape=shape,
-            **dims,  # type: ignore[arg-type]
+            shape=self._read_shape(),
         )
 
+    def _read_shape(self) -> PipeShape | AngleShape | RectShape | None:
+        """Build the display-only shape hint from the form fields.
+
+        Dimensions are optional in the UI, so an incomplete shape degrades
+        to ``None`` instead of raising — the hint is never emitted to
+        OpenSees and cannot change an analysis result.
+        """
+
+        def dim(key: str) -> float | None:
+            return _opt_value(self._dim_spins[key])
+
+        kind = self._shape.currentData()
+        if kind == "rect":
+            b, d = dim("b"), dim("d")
+            if b is None or d is None:
+                return None
+            return RectShape(b=b, d=d)
+        if kind == "angle":
+            b, d, t = dim("b"), dim("d"), dim("t")
+            if b is None or d is None or t is None:
+                return None
+            return AngleShape(b=b, d=d, t=t)
+        if kind == "pipe":
+            od, t = dim("od"), dim("t")
+            if od is None or t is None:
+                return None
+            return PipeShape(od=od, t=t)
+        return None
+
 
 class FiberSectionSummaryForm(SectionFormBase):
     """Read-only overview of a :class:`FiberSection`.