On Windows, subprocess text=True without an explicit encoding decodes
child output with the ANSI code page (e.g. 'gbk'); non-ASCII bytes then
raise UnicodeDecodeError inside subprocess._readerthread, killing the
Hermes backend before it becomes ready and surfacing as the desktop boot
timeout.
Sweep every hermes_cli text=True subprocess call to encoding='utf-8',
errors='replace', and add an AST-based regression test that fails when a
future text-mode call omits the encoding.
Fixes#55658
