Add kernel solid operations and complete Solid3D (create and rigid move)

An additive HostApi::solid_operation builds cadkernel primitives and applies
rigid transforms, verifying each result lifts back losslessly and refusing a
payload it cannot lift. Exposed as doc.solids in Python; Solid3D, Body and
Region are mapped read-only with the opaque payload preserved. The lifecycle
test passes through the real runner with analytic volumes and exact extents as
oracles, DWG and DXF reopen with re-edit, and undo restores exactly.

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

crates/ocs_plugin_api/entity_coverage_policy.json

@@ -493,6 +493,15 @@
       "lower_right_corner",
       "lock_aspect",
       "is_paper_space"
+    ],
+    "Solid3D": [
+      "layer"
+    ],
+    "Body": [
+      "layer"
+    ],
+    "Region": [
+      "layer"
     ]
   },
   "readable": {
@@ -603,6 +612,21 @@
       "source_application",
       "ole_object_type",
       "dwg_mode"
+    ],
+    "Solid3D": [
+      "uid",
+      "point_of_reference",
+      "history_handle"
+    ],
+    "Body": [
+      "uid",
+      "point_of_reference",
+      "history_handle"
+    ],
+    "Region": [
+      "uid",
+      "point_of_reference",
+      "history_handle"
     ]
   },
   "aliases": {