feat(environment): portable layer states, named views and UCS on both engines

Layer states are ACADMCP_LAYERSTATES XRECORD chunks (<= 255 ASCII chars each),
in the file and not in AutoCAD's Layer States Manager. Headless view restore
writes the *Active VPORT (ezdxf's header has no $VIEWCTR; measured). UCS is
stored and made current; tool coordinates stay WCS.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

engineering/environment/__init__.py

@@ -0,0 +1,16 @@
+"""Environment helpers (v1.6 track E): portable layer states, view and UCS
+argument resolution. Pure data and validation — no ezdxf, no COM."""
+
+from .layer_states import (  # noqa: F401
+    DICT_NAME,
+    PROPERTIES,
+    decode_state,
+    diff_snapshot,
+    encode_state,
+    snapshot_from_layers,
+    validate_properties,
+    validate_state_name,
+)
+from .names import validate_name  # noqa: F401
+from .ucs import WORLD, resolve_ucs_axes  # noqa: F401
+from .views import resolve_view_args  # noqa: F401