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/modules/draw/modify/geom.rs

@@ -1,4 +1,4 @@
-//! Adapters between the editing commands and `cadkernel`'s plane geometry.
+//! Adapters between the editing commands and `opencadkernel`'s plane geometry.
 //!
 //! The kernel takes points as `[f64; 2]` and hands tessellation back as
 //! `[f64; 3]`. The commands here grew up passing loose `x, y` scalars and
@@ -11,11 +11,11 @@
 //! resident render path splits the `f64` into a high/low pair instead. Only a
 //! caller knows which of the two it is.
 
-use cadkernel::geom2d::{self, Ellipse};
+use kernel::geom2d::{self, Ellipse};
 
 /// Re-exported unchanged: these already speak in plain `f64`, so there is no
 /// call-shape difference for this module to absorb.
-pub use cadkernel::geom2d::{arc_parameter, lerp, normalize_angle};
+pub use kernel::geom2d::{arc_parameter, lerp, normalize_angle};
 
 /// Preview geometry keeps the density the commands have always used.
 const SEGMENTS_PER_RADIAN: f64 = geom2d::DEFAULT_SEGMENTS_PER_RADIAN;