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>

crates/ocs_plugin_api/src/lib.rs

@@ -2,7 +2,7 @@
 //!
 //! The stable, semver-versioned contract an add-on package targets instead of
 //! the `OpenCADStudio` binary internals. It is intentionally **dependency
-//! free** (no `iced`, no `acadrust`) so engine crates and external tooling can
+//! free** (no `iced`, no `opencadcodec`) so engine crates and external tooling can
 //! depend on it cheaply.
 //!
 //! Two pieces live here:
@@ -13,12 +13,12 @@
 //!   ([`RibbonGroup`], [`ToolDef`], …) a plugin uses to describe its tab.
 //!
 //! The runtime host surface a plugin uses at *dispatch* time (document access,
-//! command line, undo) is `acadrust`-typed and therefore lives in the `host`
-//! feature; it re-exports `acadrust` so plugins do not need to depend on it
+//! command line, undo) is `opencadcodec`-typed and therefore lives in the `host`
+//! feature; it re-exports `opencadcodec` so plugins do not need to depend on it
 //! directly and risk an ABI mismatch from a different version.
 //!
 //! For binary compatibility, the host and every plugin must resolve the same
-//! `acadrust` source. The host does this via a `[patch.crates-io]` entry in
+//! `opencadcodec` source. The host does this via a `[patch.crates-io]` entry in
 //! `Cargo.toml`; out-of-tree plugins should copy that exact patch.
 //!
 //! For internal architecture (process model, wire protocols, versioning policy,
@@ -40,7 +40,7 @@ pub mod entity_coverage;
 pub mod entity_coverage_types;
 pub mod version_info;
 
-/// Runtime host surface — only built with the `host` feature (pulls `acadrust`).
+/// Runtime host surface — only built with the `host` feature (pulls `opencadcodec`).
 #[cfg(feature = "host")]
 pub mod host;