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/update/command.rs

@@ -168,10 +168,9 @@ pub(super) fn on_tab_close(&mut self, idx: usize) -> Task<Message> {
                     }
                     // A typed grip-menu value reshapes dimensions too — drop a
                     // stale baked *D block (no-op for non-dims). (#398)
-                    crate::modules::draw::modify::explode::invalidate_dim_block(
-                        &mut self.tabs[i].scene.document,
-                        pending.handle,
-                    );
+                    self.tabs[i]
+                        .scene
+                        .invalidate_dim_block_recorded(pending.handle);
                     self.tabs[i].scene.bump_geometry();
                     self.tabs[i].dirty = true;
                     self.refresh_selected_grips();
@@ -987,10 +986,9 @@ pub(super) fn on_tab_close(&mut self, idx: usize) -> Task<Message> {
                 }
                 // Menu actions reshape dimensions too — drop a stale baked *D
                 // block so the edit is visible (no-op for non-dims). (#398)
-                crate::modules::draw::modify::explode::invalidate_dim_block(
-                    &mut self.tabs[i].scene.document,
-                    popup.handle,
-                );
+                self.tabs[i]
+                    .scene
+                    .invalidate_dim_block_recorded(popup.handle);
                 self.tabs[i].scene.bump_geometry();
                 self.tabs[i].dirty = true;
                 self.refresh_selected_grips();
@@ -1918,7 +1916,7 @@ pub(super) fn on_tab_close(&mut self, idx: usize) -> Task<Message> {
             self.tabs[i].dirty = true;
         } else {
             // Nothing changed — drop the snapshot pushed a moment ago.
-            let _ = self.tabs[i].history.undo_stack.pop();
+            self.discard_last_undo_entry(i);
         }
         self.refresh_properties();
         Task::none()

src/app/update/mod.rs

@@ -134,6 +134,9 @@ impl OpenCADStudio {
             }
         }
         let task = self.update_inner(msg);
+        // Close the document-level first-touch transaction started by
+        // push_undo_snapshot at this message boundary.
+        self.finish_all_pending_history();
         // After every message, mirror the active command step's prompt so
         // its history line stays pinned (non-fading) until the step changes.
         let prompt = self.tabs[self.active_tab]
@@ -2228,7 +2231,7 @@ 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/update/viewport.rs

@@ -1932,29 +1932,20 @@ impl OpenCADStudio {
             // once, dropping the overlay preview.
             if let Some(h) = self.grip_preview_handle.take() {
                 // Undo entry for the drag (#332): the pre-drag backup
-                // swaps in, the PRE state is snapshotted, then the
-                // dragged result swaps back. Without this a grip edit
-                // (e.g. reshaping a polyline vertex) was un-undoable —
-                // the drag mutated the document without any history.
+                // and live dragged image form a one-entity Arc delta. The old
+                // swap/full-document snapshot made a vertex drag O(document).
                 if let Some(orig) = self.grip_original.take() {
-                    if let Some(e) = self.tabs[i].scene.document.get_entity_mut(h) {
-                        let dragged = std::mem::replace(e, orig);
-                        let snap = self.capture_history_snapshot(i, "GRIP");
-                        if let Some(e2) = self.tabs[i].scene.document.get_entity_mut(h) {
-                            *e2 = dragged;
-                        }
-                        self.tabs[i].history.undo_stack.push(snap);
-                        self.tabs[i].history.redo_stack.clear();
-                        self.tabs[i].dirty = true;
-                    }
+                    self.push_single_entity_history(i, "GRIP", h, std::sync::Arc::new(orig));
+                    self.tabs[i].dirty = true;
                 }
                 self.grip_text_verts = Vec::new();
                 self.grip_text_slide = false;
                 self.tabs[i].scene.hidden.remove(&h);
                 self.tabs[i].scene.clear_preview_wire();
                 // Only the dragged entity changed — re-tessellate just it.
-                self.tabs[i].scene.mark_entity_dirty(h);
-                self.tabs[i].scene.bump_geometry_no_blocks();
+                self.tabs[i]
+                    .scene
+                    .bump_entities(&[(h, crate::scene::ChangeKind::Modified)]);
             }
             // Placement confirmed — keep the just-added leader.
             self.grip_add_provisional = None;