On Windows with non-UTF-8 console encodings (e.g. cp949, cp1252),
StreamHandler emits raise UnicodeEncodeError when log messages contain
characters outside the console codepage — such as the em-dash (U+2014)
in the session hygiene message.
This crashed the gateway process silently, leaving no diagnostic output.
Fix: add _safe_stderr() helper that wraps sys.stderr in a TextIOWrapper
with encoding='utf-8' and errors='replace' when the console encoding
is not UTF-8. Applied to both:
- hermes_logging.py setup_verbose_logging() stderr handler
- gateway/run.py optional stderr handler
The wrapper ensures log lines are never lost — un-encodable characters
are replaced with '?' instead of crashing the process.
Fixes#40432
b08662b782