perf: make edit history incremental

Replace full-document snapshots with Arc first-touch deltas and batch cache invalidation. Reuse interaction and GPU category caches across unrelated edits.

src/app/commands/draw.rs

@@ -715,7 +715,7 @@ impl OpenCADStudio {
                     // Stash the erased entities so OOPS can restore them.
                     self.oops_cache = handles
                         .iter()
-                        .filter_map(|h| self.tabs[i].scene.document.get_entity(*h).cloned())
+                        .filter_map(|h| self.tabs[i].scene.document.get_entity_arc(*h))
                         .collect();
                     self.tabs[i].scene.erase_entities(&handles);
                     self.tabs[i].dirty = true;

src/app/commands/fileops.rs

@@ -78,15 +78,15 @@ impl OpenCADStudio {
                 if self.oops_cache.is_empty() {
                     self.command_line.push_info("OOPS: nothing to restore.");
                 } else {
-                    self.push_undo_snapshot(i, "OOPS");
                     let restored = std::mem::take(&mut self.oops_cache);
+                    let pending = self.begin_undo(i, "OOPS", restored.len(), true);
+                    let restored = self.tabs[i].scene.restore_erased_entities(restored);
                     let n = restored.len();
-                    for e in restored {
-                        self.tabs[i].scene.add_entity_clone(e);
-                    }
-                    self.tabs[i].scene.bump_geometry();
                     self.tabs[i].dirty = true;
                     self.refresh_properties();
+                    if let Some(pending) = pending {
+                        self.commit_undo_delta(i, pending);
+                    }
                     self.command_line
                         .push_output(&format!("OOPS: restored {n} object(s)."));
                 }

src/app/commands/styleprops.rs

@@ -1785,7 +1785,7 @@ impl OpenCADStudio {
                         self.command_line
                             .push_output(&format!("RENAME: '{}' → '{}'.", old_name, new_name));
                     } else {
-                        let _ = self.tabs[i].history.undo_stack.pop();
+                        self.discard_last_undo_entry(i);
                         if !known {
                             self.command_line.push_error(&format!("RENAME: unknown type '{}'. Use LAYER BLOCK STYLE DIMSTYLE LINETYPE UCS VIEW", type_str));
                         } else if type_str == "BLOCK" {