feat(input): lock the next point to a typed <angle

Typing <angle at a point prompt (e.g. <30) now fixes the direction of
the next point from the last one until a point is placed: the cursor
moves along that direction, and a bare number entered next is the
distance along it. The angle is read in the drawing's angle base and
direction and turned into the current UCS. Works from the command line
and from scripts or the automation token input alike.

Fixes #1464

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/update/dynamic.rs

@@ -29,6 +29,10 @@ impl OpenCADStudio {
         &self,
         i: usize,
     ) -> Option<(glam::DVec3, glam::DVec3)> {
+        // A typed `<angle` locks the way from the last point.
+        if let (Some(dir), Some(base)) = (self.angle_override, self.last_point) {
+            return Some((base, dir));
+        }
         // OTRACK already exposes its acquired world-space ray.
         if let Some((base, dir)) = self.otrack_active {
             return Some((base, dir));