Feat: Phase 5 — MLine, Tolerance render; DimStyle Choice picker on dimensions

- mline.rs: MLine renders center spine + two parallel offset lines at
  ±scale/2 using the vertex miter directions; vertex grips; scale,
  closed and style-name properties
- tolerance.rs: Tolerance renders the GDT text string via font
  tessellation at insertion_point with rotation from direction vector;
  insertion grip and position properties
- properties.rs: Dimension entity's style_name EditText is upgraded to
  a Choice dropdown when document.dim_styles is non-empty, enabling
  point-and-click DimStyle assignment without a separate panel

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/entities/traits.rs

@@ -50,6 +50,8 @@ impl EntityTypeOps for EntityType {
             EntityType::Wipeout(wo) => TruckConvertible::to_truck(wo, document),
             EntityType::AttributeDefinition(a) => TruckConvertible::to_truck(a, document),
             EntityType::AttributeEntity(a) => TruckConvertible::to_truck(a, document),
+            EntityType::MLine(ml) => TruckConvertible::to_truck(ml, document),
+            EntityType::Tolerance(tol) => TruckConvertible::to_truck(tol, document),
             EntityType::Text(text) => TruckConvertible::to_truck(text, document),
             EntityType::MText(text) => TruckConvertible::to_truck(text, document),
             EntityType::Leader(leader) => TruckConvertible::to_truck(leader, document),
@@ -74,6 +76,8 @@ impl EntityTypeOps for EntityType {
             EntityType::Wipeout(wo) => Grippable::grips(wo),
             EntityType::AttributeDefinition(a) => Grippable::grips(a),
             EntityType::AttributeEntity(a) => Grippable::grips(a),
+            EntityType::MLine(ml) => Grippable::grips(ml),
+            EntityType::Tolerance(tol) => Grippable::grips(tol),
             EntityType::Point(pt) => Grippable::grips(pt),
             EntityType::Spline(spline) => Grippable::grips(spline),
             EntityType::Text(text) => Grippable::grips(text),
@@ -143,6 +147,14 @@ impl EntityTypeOps for EntityType {
                 a,
                 text_style_names,
             )),
+            EntityType::MLine(ml) => Some(PropertyEditable::geometry_properties(
+                ml,
+                text_style_names,
+            )),
+            EntityType::Tolerance(tol) => Some(PropertyEditable::geometry_properties(
+                tol,
+                text_style_names,
+            )),
             EntityType::Hatch(hatch) => Some(PropertyEditable::geometry_properties(
                 hatch,
                 text_style_names,
@@ -202,6 +214,8 @@ impl EntityTypeOps for EntityType {
             EntityType::Wipeout(wo) => PropertyEditable::apply_geom_prop(wo, field, value),
             EntityType::AttributeDefinition(a) => PropertyEditable::apply_geom_prop(a, field, value),
             EntityType::AttributeEntity(a) => PropertyEditable::apply_geom_prop(a, field, value),
+            EntityType::MLine(ml) => PropertyEditable::apply_geom_prop(ml, field, value),
+            EntityType::Tolerance(tol) => PropertyEditable::apply_geom_prop(tol, field, value),
             EntityType::Hatch(hatch) => PropertyEditable::apply_geom_prop(hatch, field, value),
             EntityType::Point(pt) => PropertyEditable::apply_geom_prop(pt, field, value),
             EntityType::Spline(spline) => PropertyEditable::apply_geom_prop(spline, field, value),
@@ -232,6 +246,8 @@ impl EntityTypeOps for EntityType {
             EntityType::Wipeout(wo) => Grippable::apply_grip(wo, grip_id, apply),
             EntityType::AttributeDefinition(a) => Grippable::apply_grip(a, grip_id, apply),
             EntityType::AttributeEntity(a) => Grippable::apply_grip(a, grip_id, apply),
+            EntityType::MLine(ml) => Grippable::apply_grip(ml, grip_id, apply),
+            EntityType::Tolerance(tol) => Grippable::apply_grip(tol, grip_id, apply),
             EntityType::Point(pt) => Grippable::apply_grip(pt, grip_id, apply),
             EntityType::Spline(spline) => Grippable::apply_grip(spline, grip_id, apply),
             EntityType::Text(text) => Grippable::apply_grip(text, grip_id, apply),
@@ -262,6 +278,8 @@ impl EntityTypeOps for EntityType {
             EntityType::Wipeout(wo) => Transformable::apply_transform(wo, t),
             EntityType::AttributeDefinition(a) => Transformable::apply_transform(a, t),
             EntityType::AttributeEntity(a) => Transformable::apply_transform(a, t),
+            EntityType::MLine(ml) => Transformable::apply_transform(ml, t),
+            EntityType::Tolerance(tol) => Transformable::apply_transform(tol, t),
             EntityType::MText(text) => Transformable::apply_transform(text, t),
             EntityType::Point(pt) => Transformable::apply_transform(pt, t),
             EntityType::Spline(spline) => Transformable::apply_transform(spline, t),