feat: node graph overlay; move to opencadcodec/opencadkernel/opencadgraph

The codec and kernel repositories and crates are renamed opencadcodec and
opencadkernel. Inside OCS they are depended on under short keys, so code
reads `codec::`, `kernel::` and the new `graph::` (opencadgraph, the node
graph engine). File-format and protocol spellings stay as they were: the
ACIS product id `acadrust`, the ACADRUST_* switches and the plugin
version keys `acadrust_version` / `acadrust_source`.

A button left of MCP on the command line opens a translucent node graph
over the viewport, with a palette of object, input, math, logic, list,
text and geometry nodes added by click or drag. An object node owns
drawing entities and its rows are the Properties panel's own rows for
them: the single-object page is extracted from refresh_properties as
entity_property_sections, values use the control protocol's
property_json, and writes go through set_property_value with a property
target override, so the panel, MCP and the graph share one read/write
path. A list reaching an object row makes one entity per element. Each
graph action is one undo step; the canvas pans and zooms.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/scene/model/hatch_model.rs

@@ -3,7 +3,7 @@
 
 use std::sync::Arc;
 
-use cadkernel::geom2d::{
+use kernel::geom2d::{
     inside_spans, Curve as KernelCurve, Line as KernelLine, Tolerance, XLine as KernelXLine,
 };
 
@@ -244,11 +244,11 @@ pub struct HatchModel {
     /// Per-ring DXF role, aligned with the NaN-separated boundary paths.
     pub boundary_exterior: Option<Arc<Vec<bool>>>,
     /// Source entity handles for each boundary ring.
-    pub boundary_sources: Option<Arc<Vec<Vec<acadrust::Handle>>>>,
+    pub boundary_sources: Option<Arc<Vec<Vec<codec::Handle>>>>,
     /// Exact boundary paths retained for persistence and editing.
-    pub boundary_paths: Option<Arc<Vec<acadrust::entities::BoundaryPath>>>,
+    pub boundary_paths: Option<Arc<Vec<codec::entities::BoundaryPath>>>,
     /// Island handling used by the persisted hatch entity.
-    pub style: acadrust::entities::HatchStyleType,
+    pub style: codec::entities::HatchStyleType,
     /// Fill pattern.
     pub pattern: HatchPattern,
     /// Catalog name for this pattern (e.g. "ANSI31", "SOLID", "LINEAR").
@@ -277,14 +277,14 @@ impl HatchModel {
         &self,
         angle_deg: f32,
         shift: f32,
-    ) -> Option<cadkernel::geom2d::GradientFrame> {
+    ) -> Option<kernel::geom2d::GradientFrame> {
         let boundary: Vec<[f64; 2]> = self
             .boundary
             .iter()
             .filter(|point| point[0].is_finite() && point[1].is_finite())
             .map(|point| [point[0] as f64, point[1] as f64])
             .collect();
-        cadkernel::geom2d::gradient_frame(
+        kernel::geom2d::gradient_frame(
             &boundary,
             (angle_deg as f64).to_radians(),
             shift as f64,
@@ -309,7 +309,7 @@ impl HatchModel {
             rings.push(ring);
         }
 
-        let (points, triangles) = cadkernel::geom2d::triangulate_rings(&rings);
+        let (points, triangles) = kernel::geom2d::triangulate_rings(&rings);
         let vertices = points
             .into_iter()
             .map(|[x, y]| [x as f32, y as f32])