Angular dimensional constraint: reference flow, dynamic angular dimension, angN parameters

DCANGULAR picks two lines, an arc or three points, takes the dimension
line location to choose the sector and the value or name, and creates the
dynamic two-line or three-point angular dimension driven by an angN
parameter. Reference messages for invalid, repeated and parallel sides,
existing names and invalid names; angle values display within one turn at
the angular precision; the first side (or vertex and first point) stays
when the value changes; the ribbon Dimensional panel follows the reference
order.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/command.rs

@@ -1630,8 +1630,26 @@ pub enum CmdResult {
         direction: Option<crate::scene::parametric_constraints::ParametricRef>,
         name: String,
         expression: String,
+        /// The user named the parameter (`name=expression`); an existing
+        /// name is then refused.
+        renamed: bool,
         label: &'static str,
     },
+    /// Adds an angular constraint with its dynamic angular dimension and
+    /// the `angN` parameter that drives it. Two lines: `refs` =
+    /// `[first_line, second_line]`, `points` = both lines' ends; three
+    /// points: `refs` = `[first, vertex, second]`, `points` =
+    /// `[vertex, first, second]`.
+    AddAngularConstraint {
+        refs: Vec<crate::scene::parametric_constraints::ParametricRef>,
+        points: Vec<DVec3>,
+        location: DVec3,
+        /// Which of the four angles the dimension line location picked.
+        sector: u8,
+        name: String,
+        expression: String,
+        renamed: bool,
+    },
     /// Aligned's 2Lines: makes `second_line` parallel to `first_line` (whose
     /// ends stay put), then hands the second line's solved ends back through
     /// `CadCommand::accept_parallel_line`.
@@ -1812,6 +1830,8 @@ pub enum CmdResult {
     ReportMeasurement(String),
     /// Print an input error and keep the command active.
     ReportError(String),
+    /// Reports an error and ends the command (`Lines are parallel.`).
+    CancelWithMessage(String),
     /// Print a measurement result, clear the current selection, and keep the command active.
     ReportMeasurementAndDeselect(String),
     /// Clear the current selection and keep the command active at its updated step.