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/names.py

@@ -0,0 +1,17 @@
+"""One rule for the names this package stores in the drawing."""
+
+from __future__ import annotations
+
+
+def validate_name(name, *, what: str, max_len: int = 255) -> str:
+    """A non-empty, stripped string without control characters, else ``ValueError``."""
+    if not isinstance(name, str):
+        raise ValueError(f"{what} must be a string, got {type(name).__name__}")
+    clean = name.strip()
+    if not clean:
+        raise ValueError(f"{what} must not be empty")
+    if len(clean) > max_len:
+        raise ValueError(f"{what} is longer than {max_len} characters")
+    if any(ord(ch) < 32 for ch in clean):
+        raise ValueError(f"{what} must not contain control characters")
+    return clean