Complete MultiLeader host model coverage

Extends the adapter generator (Color, LineWeight, mixed unit/payload enums,
fixed float arrays, bitflags-2 newtypes, keep_types override) and maps
MultiLeader with a merge-style context patch, host validation and
reference checks. staged_python_multileader_lifecycle_over_real_ipc passes
the full gate including DWG and DXF reopen.

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

plugins/opencad-python/src/ocs_module.rs

@@ -3188,6 +3188,18 @@ mod ocs {
         })
     }
 
+    fn py_to_f64_array<const N: usize>(value: PyObjectRef, vm: &VirtualMachine) -> PyResult<[f64; N]> {
+        let items: Vec<PyObjectRef> = value.try_into_value(vm)?;
+        if items.len() != N {
+            return Err(vm.new_value_error(format!("expected {N} numbers, got {}", items.len())));
+        }
+        let mut out = [0.0; N];
+        for (slot, item) in out.iter_mut().zip(items) {
+            *slot = py_number_to_f64(item, vm)?;
+        }
+        Ok(out)
+    }
+
     /// Accept a Python int or float; `try_into_value::<f64>` rejects ints.
     fn py_number_to_f64(value: PyObjectRef, vm: &VirtualMachine) -> PyResult<f64> {
         Ok(value.try_float(vm)?.to_f64())
@@ -3249,6 +3261,7 @@ mod ocs {
 
     include!(concat!(env!("OUT_DIR"), "/entity_crud.rs"));
     include!("dimension_model.rs.inc");
+    include!("patch_helpers.rs.inc");
 
     // ════════════════════════════════════════════════════════════════════
     // Phase 1 — wiring the generic conversion functions above into `ocs`.
@@ -4743,7 +4756,7 @@ mod tests {
                 );
             }
         }
-        assert_eq!(emitted.len(), 25);
+        assert_eq!(emitted.len(), 26);
     }
 
     #[cfg(feature = "experimental-host-model")]

plugins/opencad-python/src/patch_helpers.rs.inc

@@ -0,0 +1,23 @@
+// Merge helpers for nested structs that scripts edit as a partial patch.
+
+/// Apply `patch` (a dict of context fields) onto `existing`, so a script can
+/// change one context field without resetting the rest. Unknown keys error.
+fn merge_multileader_context(
+    existing: &acadrust::entities::MultiLeaderAnnotContext,
+    patch: PyObjectRef,
+    vm: &VirtualMachine,
+) -> PyResult<acadrust::entities::MultiLeaderAnnotContext> {
+    let patch = patch.try_into_value::<rustpython_vm::builtins::PyDictRef>(vm)?;
+    let merged = multi_leader_annot_context_to_dict(vm, existing)?
+        .try_into_value::<rustpython_vm::builtins::PyDictRef>(vm)?;
+    for key in patch.keys_vec() {
+        let name = key.clone().try_into_value::<String>(vm)?;
+        if merged.get_item_opt(name.as_str(), vm)?.is_none() {
+            return Err(vm.new_value_error(format!(
+                "ocs: MultiLeader.context property {name:?} is outside the editable schema"
+            )));
+        }
+        merged.set_item(name.as_str(), patch.get_item(name.as_str(), vm)?, vm)?;
+    }
+    dict_to_multi_leader_annot_context(merged.into(), vm)
+}