Two Windows fixes for the canonical test runner, salvaged from #66496:
- scripts/run_tests.sh: probe the native Windows venv layout
(Scripts/activate → Scripts/python.exe) alongside bin/activate,
adapted to main's pytest-import-guarded loop with SKIPPED_VENVS
reporting. Without it a python -m venv / uv venv on Git Bash/MSYS is
never found and the runner refuses to start.
- scripts/run_tests_parallel.py: _make_stdio_glyph_safe() reconfigures
stdout/stderr to UTF-8 (errors=replace fallback) so the ✓/✗ progress
glyphs cannot crash a cp1252 console when the runner is invoked
directly (run_tests.sh's PYTHONUTF8=1 only covers the wrapped path).
No-op on UTF-8 stdio. Ships 3 OS-independent cp1252 tests plus
encoding=utf-8 in the runner-subprocess assertions.
Dropped from the original PR: the USERPROFILE/HOMEDRIVE/HOMEPATH/
SYSTEMROOT env-forwarding hunk — main's WIN_ENV loop already forwards
a superset (#67385/#70813).
