feat(properties): rework Text/MText/MLeader/Leader panels to standard layout

Match the entity Properties panels to the standard CAD layout and
web-verified behaviour:

- Text: combined Justify (horizontal x vertical) dropdown; Position and
  Text-alignment rows become editable/grayed by justification; drop the
  Annotative-scale row.
- MText: combined Justify; editable Direction, Line space distance
  (back-solves the factor) and Line space style; Defined width/height
  gated on column mode.
- MLeader: regrouped to match the palette - drop the Leader Structure
  group (fold landing rows into Leaders), gate Text vs Block on content
  type, full 9-value attachment label set, resolve handle-backed rows
  (style, text style, arrowhead, linetype) to names.
- Leader: Lines & Arrows / Text / Fit are resolved from the dimension
  style (arrowhead, arrow size, dim-line lineweight/colour, text gap,
  vertical text pos, overall scale); Current Vertex navigator; combined
  Type; Geometry group after General; no 3D-Visualisation group.
- General: rename "LT Scale" to "Linetype scale"; show ByLayer
  transparency by name. Add shared num_prop helper for conditionally
  editable numeric rows.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/entities/common.rs

@@ -193,6 +193,18 @@ pub fn ro_prop(label: &'static str, field: &'static str, value: impl Into<String
     }
 }
 
+/// A numeric row that is an editable box when `editable`, otherwise a grayed
+/// read-only value using the same length formatting. Used where a field's
+/// editability depends on entity state (e.g. a text point that is only live for
+/// certain justifications, or an MText column dimension).
+pub fn num_prop(label: &'static str, field: &'static str, value: f64, editable: bool) -> Property {
+    if editable {
+        edit_prop(label, field, value)
+    } else {
+        ro_prop(label, field, format_length(value))
+    }
+}
+
 /// A ◀ / ▶ index navigator row (e.g. a polyline's Current Vertex). `display` is
 /// the label shown between the arrows (e.g. "2 / 7").
 pub fn stepper_prop(