feat(grip): popup menus for polylines, spline, mline, hatch, leaders, text

Vocabulary added: AddFitPoint, RemoveFitPoint, Refit, RefineVertices,
TangentDirection, MoveWithText, StackText, UnstackText.

Polyline/Polyline2D/Polyline3D: vertex Add/Remove. MLine: same.
Spline: CV Add/Remove plus Refine Vertices (chord-midpoint insertion,
weights kept in sync, knots cleared so to_truck rebuilds uniform vec).
Hatch: centroid Origin/Angle/Scale (Angle and Scale prompt for value).
Leader: vertex Add/Remove (arrow + centroid stay Stretch-only).
MultiLeader: vertex Add/Remove Leader; MText location Move-with-Leader /
Move-Independent (menu live, structural edits stubbed). Text/MText:
Rotate prompts for degrees and sets rotation.

Spline, Leader, MultiLeader switched from impl_entity_basics! to manual
trait impls so grip_menu can be overridden.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/scene/object.rs

@@ -137,4 +137,11 @@ pub enum GripMenuAction {
     HatchScale,
     HatchPattern,
     TangentDirection,
+    AddFitPoint,
+    RemoveFitPoint,
+    Refit,
+    RefineVertices,
+    MoveWithText,
+    StackText,
+    UnstackText,
 }