refactor: remove remaining world_offset vestiges in app/

Clean up the last zero-valued world_offset locals outside the scene
tessellation core: the UCS wire-affine / grid-basis origin shift
(document.rs), the coordinate readout (view.rs), grip absolute-apply
(update.rs), the dead properties-edit re-offset guard, the MTEXT preview
glyph-box shift (mtext_editor.rs), and the cross-drawing paste correction
(commands.rs / cmd_result.rs) — including the now-dead
`clipboard_world_offset` field. Coordinates are absolute throughout.

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

src/app/document.rs

@@ -288,11 +288,10 @@ impl DocumentTab {
             return glam::Mat4::IDENTITY;
         }
         let (o, x, y, z) = self.ucs_xform().axes();
-        let wo = [0.0_f64; 3];
         let origin = glam::Vec3::new(
-            o.x - wo[0] as f32,
-            o.y - wo[1] as f32,
-            o.z - wo[2] as f32,
+            o.x as f32,
+            o.y as f32,
+            o.z as f32,
         );
         glam::Mat4::from_cols(
             x.extend(0.0),
@@ -321,11 +320,10 @@ impl DocumentTab {
         }
         let xf = self.ucs_xform();
         let (o, ..) = xf.axes();
-        let wo = [0.0_f64; 3];
         let origin = glam::Vec3::new(
-            o.x - wo[0] as f32,
-            o.y - wo[1] as f32,
-            o.z - wo[2] as f32,
+            o.x as f32,
+            o.y as f32,
+            o.z as f32,
         );
         (origin, xf.rotation_mat())
     }