Merge PR #1028: add document API with atomic edits

Add the typed document facade and plugin IPC adapter. Prepare bulk edits
before mutation, preserve undo and dirty state, keep profile elevations,
validate numeric inputs and session bindings, and generate Python constructors
with typed results.

Reuse existing entity transforms and profile conversion. Compute mass
properties and closed-surface bounds in cadkernel; pin its main revision
6a5e6fc2822f6af6b2611cd605b44437b35158f0. Keep plugin API metadata at version 6.

Validation: 646 native application tests, 597 kernel tests, 12 document API
tests, 91 plugin API tests, 3 Python tests, default/IPC feature builds and
wasm32 check passed.

crates/ocs_plugin_api/src/host.rs

@@ -552,6 +552,18 @@ pub trait HostApi {
         let _ = tab_id;
         None
     }
+
+    /// DocApi v2 (`ocs_doc_api`): dispatch one bincode-serialized `DocApiEnvelope`
+    /// (one write op OR a read-only query batch) and return the bincode-serialized
+    /// `Result<Receipt, ApiError>`. Opaque bytes:
+    /// this crate does not depend on `ocs_doc_api`, it only routes the envelope.
+    ///
+    /// Added for the DocApi v2 adapter. The default returns `Err` ("not supported");
+    /// the in-process host (`HostSession`) overrides it to call the DocApi executor.
+    fn doc_api_dispatch(&mut self, tab_id: u64, bytes: &[u8]) -> Result<Vec<u8>, String> {
+        let _ = (tab_id, bytes);
+        Err("DocApi v2 not supported by this host".to_string())
+    }
 }
 
 /// Simplified, read-only entity kind exposed by [`DocumentReader`].