fix(props): angle rows format via AUNITS, not LUNITS (#297)

Every angle row went through the linear formatter, so switching LUNITS
to Architectural showed a block's Rotation as feet-and-inches — and the
string wouldn't parse back, wedging the field until it was cleared and
retyped. Only the decimal/fractional LUNITS survived by accident.

New edit_angle row helper formats angles with format_angle
(AUNITS/AUPREC: decimal degrees, DMS, grads or radians), applied to all
17 angle rows (rotations, obliquing, arc start/end, hatch pattern
angle, multileader text rotation). parse_angle_deg converts every
AUNITS display form back to degrees ("30°"/"30d", DMS 30°15'20",
33.33g, 0.52r) and parse_f64 falls back to it, so the displayed value
round-trips through an edit.

Closes #297

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

src/entities/mtext.rs

@@ -2,7 +2,7 @@ use acadrust::entities::{AttachmentPoint, DrawingDirection, MText};
 
 use crate::command::EntityTransform;
 use crate::entities::common::{
-    edit_prop as edit, num_prop as num_row, ro_prop as ro, square_grip, triangle_grip,
+    edit_angle_prop as edit_angle, edit_prop as edit, num_prop as num_row, ro_prop as ro, square_grip, triangle_grip,
 };
 use crate::entities::text_support::{
     layout_mtext, resolve_text_style, GlyphBox, MTextColumns, MTextRenderOpts, MTextVAnchor,
@@ -275,7 +275,7 @@ fn properties(t: &MText, text_style_names: &[String]) -> Vec<PropSection> {
                     },
                 },
                 edit("Text height", "height", t.height),
-                edit("Rotation", "rotation", t.rotation.to_degrees()),
+                edit_angle("Rotation", "rotation", t.rotation.to_degrees()),
                 edit("Line space factor", "line_spacing", t.line_spacing_factor),
                 edit("Line space distance", "line_space_distance", line_space_distance),
                 Property {