Merge pull request #1447 from ramox81:codex/diameter-constraint-parity

#1447 branched from the same commit as #1443 and rewrote the radial
dimensional constraint a second time, so the two designs had to be
reconciled rather than stacked. #1447's is the one kept: it covers
DCRADIUS and DCDIAMETER through one command, places the dimension by the
direction the location was picked in rather than storing a text point,
and names the parameters `radN` / `diaN`. #1443's radial command result,
its entity builder call and its follow-up code are gone; its own
independent work stays — the ribbon's small-button grid and tool
descriptions, the magnitude reading of a negative radius, and the centre
anchor a parameter edit resizes a circle about.

The DIMCONSTRAINT default follows #1443: running DCRADIUS or DCDIAMETER
directly leaves it alone, and the Dispatch arm sets it when DIMCONSTRAINT
is what asked for the command.

The second commit's radial drawing — the dimension line broken around the
text, the elbowed leader, the centre-mark and arrowhead rules — applied to
every radius and diameter dimension, not just a constraint's, and three
layout-parity tests said the old layout was the measured one. It is now
scoped to a dimensional constraint's own dimension, as #1443 scoped its
version, and ordinary radial dimensions draw as they did.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/modules/annotate/diameter_dim.rs

@@ -87,6 +87,25 @@ impl DiameterDimensionCommand {
     }
 }
 
+/// A diameter dimension for a dimensional constraint: the dimension line
+/// runs through the centre towards `location`, and the style places the
+/// text.
+pub(crate) fn diameter_constraint_entity(
+    center: DVec3,
+    radius: f64,
+    location: DVec3,
+    text: Option<String>,
+) -> Option<EntityType> {
+    let direction = super::radius_dim::radial_direction(center, location)?;
+    let chord = center + direction * radius;
+    let far_chord = center - direction * radius;
+    let mut dim = DimensionDiameter::new(v3(chord), v3(far_chord));
+    dim.leader_length = chord.distance(location).max(radius * 0.5);
+    dim.base.actual_measurement = dim.measurement();
+    crate::entities::dimension::set_dimension_text_override(&mut dim.base, text);
+    Some(EntityType::Dimension(Dimension::Diameter(dim)))
+}
+
 impl CadCommand for DiameterDimensionCommand {
     fn set_working_plane(&mut self, _plane: WorkingPlane) {
     }

src/modules/annotate/radius_dim.rs

@@ -96,6 +96,31 @@ pub(crate) fn radial_dimension_entity(
     plane.place_entity(EntityType::Dimension(Dimension::Radius(dim)))
 }
 
+/// A radius dimension for a dimensional constraint: the leader leaves the
+/// centre towards `location`, and the style places the text.
+pub(crate) fn radius_constraint_entity(
+    center: DVec3,
+    radius: f64,
+    location: DVec3,
+    text: Option<String>,
+) -> Option<EntityType> {
+    let direction = radial_direction(center, location)?;
+    let chord = center + direction * radius;
+    let mut dim = DimensionRadius::new(v3(center), v3(chord));
+    dim.base.definition_point = v3(chord);
+    dim.leader_length = chord.distance(location).max(radius * 0.5);
+    dim.base.actual_measurement = dim.measurement();
+    crate::entities::dimension::set_dimension_text_override(&mut dim.base, text);
+    Some(EntityType::Dimension(Dimension::Radius(dim)))
+}
+
+/// The unit direction a radial constraint's dimension points in, from the
+/// centre to where its dimension line was picked.
+pub(crate) fn radial_direction(center: DVec3, location: DVec3) -> Option<DVec3> {
+    let delta = location - center;
+    (delta.length() > 1.0e-9).then(|| delta.normalize())
+}
+
 impl CadCommand for RadiusDimensionCommand {
     fn set_working_plane(&mut self, _plane: WorkingPlane) {
     }