Release snapshot pre refactor

Write PET log file as UTF-8

FileHandler used the OS default encoding, which on Windows is a legacy
codepage (cp1252) that cannot encode the box-drawing characters in the
timestamps and tables. Every record raised UnicodeEncodeError inside the
handler, so the log file was left empty while the run carried on.

No effect on Linux, where UTF-8 is already the default.

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