Merge branch 'main' into feature/parametric-constraint-system

Brings in 54 commits from origin/main: a selection-performance overhaul,
surface thickening, GPU-native wide/tapered stroke rendering, continued
ocs_doc_api evolution, and assorted fixes/polish (block double-click
editing, DWG hatch/database repair, clipboard, collapsible Properties
sections).

Six real conflicts, all where this branch had independently re-applied
a fix upstream later revised or already carried natively:

- src/app/automation.rs, src/app/command_driver.rs: combined both
  sides — kept this branch's sketch-constraint/named-parameter loading
  on "new"/"open", adopted main's Scene::clear()/material_base_dir and
  its newer rebuild_derived_caches() over the older bump_geometry().
  Scene::clear() (src/scene/entity.rs) now also resets
  sketch_constraints/named_parameters, so every caller gets this for
  free instead of each call site repeating it.
- src/io/mod.rs, src/scene/render_graph.rs: adopted main's design
  outright (commit 973af87d, authored by Hakan directly) — a large
  MINSERT is no longer purged as "corrupt" at load, only its rendering
  is bounded, preserving the source data. This branch's own earlier
  design (reject at load) predates that revision.
- src/scene/pipeline/mesh_gpu.rs: adopted main's valid_rgba_size()
  guard (a real robustness improvement over this branch's version).
- src/snap.rs: replaced wholesale with main's version — this branch's
  copy was an explicit verbatim snapshot from an earlier upstream PR
  (commit 4c264b8c) with zero constraint-system-specific content, and
  main has since evolved it considerably further.

Also removed two now-dead duplicates the merge surfaced without a
conflict marker (both branches had independently fixed the same
things): the OPTIONS/OP command dispatch/autocomplete entries, and
automation.rs's open_finalizes_and_purges_like_the_ui_open_path test
(kept main's version, which covers strictly more: solid_models/
material_base_dir reset on "new").

Full workspace suite passes (812 lib tests + this branch's own 24
constraint/persistence integration tests) except the one pre-existing,
unrelated font-test failure already present on main. Zero clippy
findings in the hand-written merge resolution itself; the ~1,171
warnings clippy reports are pre-existing in the 54 absorbed commits,
not introduced here.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/commands/draw.rs

@@ -1400,6 +1400,64 @@ impl OpenCADStudio {
                 }
             }
 
+            "SECTIONPLANE" => {
+                use crate::modules::model::sectionplane_cmd::SectionPlaneCommand;
+                let (bounds, next_name) = {
+                    let scene = &mut self.tabs[i].scene;
+                    let solid_handles = scene
+                        .document
+                        .entities()
+                        .filter_map(|entity| {
+                            matches!(
+                                entity,
+                                acadrust::EntityType::Solid3D(_)
+                                    | acadrust::EntityType::Surface(_)
+                                    | acadrust::EntityType::Region(_)
+                                    | acadrust::EntityType::Body(_)
+                            )
+                            .then_some(entity.common().handle)
+                        })
+                        .collect::<Vec<_>>();
+                    scene.restore_solid_models(&solid_handles);
+                    let bounds = solid_handles
+                        .iter()
+                        .filter_map(|handle| scene.solid_models.get(handle))
+                        .filter_map(crate::scene::model::solid_model::extent)
+                        .fold(None::<(glam::DVec3, glam::DVec3)>, |bounds, (low, high)| {
+                            let low = glam::DVec3::from_array(low);
+                            let high = glam::DVec3::from_array(high);
+                            Some(match bounds {
+                                None => (low, high),
+                                Some((min, max)) => (min.min(low), max.max(high)),
+                            })
+                        });
+                    let next_name = scene
+                        .document
+                        .entities()
+                        .filter_map(|entity| {
+                            let acadrust::EntityType::Extended(extended) = entity else {
+                                return None;
+                            };
+                            let acadrust::entities::ExtendedEntityData::SectionObject(data) =
+                                &extended.data
+                            else {
+                                return None;
+                            };
+                            data.name
+                                .strip_prefix("Section Plane (")
+                                .and_then(|name| name.strip_suffix(')'))
+                                .and_then(|name| name.parse::<usize>().ok())
+                        })
+                        .max()
+                        .unwrap_or(0)
+                        + 1;
+                    (bounds, next_name)
+                };
+                let command = SectionPlaneCommand::new(bounds, next_name);
+                self.command_line.push_info(&command.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(command));
+            }
+
             // 3DALIGN <18 numbers> — align the selected solid by 3 source→3 dest points.
             cmd if cmd == "3DALIGN"
                 || cmd == "ALIGN3D"