On Windows, Python defaults to cp1252 encoding when no encoding is
specified. JSON files containing UTF-8 characters (e.g., non-ASCII
characters) cause UnicodeDecodeError when read with cp1252.
This fixes the error that occurs when loading blueprint subgraphs
on Windows systems.
https://claude.ai/code/session_014WHi3SL9Gzsi3U6kbSjbSb
Co-authored-by: Claude <noreply@anthropic.com>