fix(windows): force utf8 for detached gateway

[embwl0x]

Fixes #60760.

Summary

• force PYTHONUTF8=1 alongside PYTHONIOENCODING=utf-8 for detached Windows gateway child environments
• cover Scheduled Task .cmd and .vbs launchers, direct detached gateway argv, and post-update windowless restart specs
• make _ensure_utf8() set UTF-8 child env defaults on Windows even when pythonw has no stdio streams to repair

Root Cause

Detached Windows gateways can run under pythonw with sys.stdout and sys.stderr set to None, so _ensure_utf8() had no stream to repair and never exported UTF-8 defaults for child processes. When a spawned child emitted UTF-8 text under a legacy ANSI locale such as GBK, Python's subprocess pipe reader could decode with the preferred locale and raise UnicodeDecodeError.

Tests

• uv run --extra dev pytest tests/hermes_cli/test_ensure_utf8_locale.py tests/hermes_cli/test_gateway_windows.py tests/tools/test_windows_native_support.py::TestWindowlessGatewayRestartSpec -q
• uv run --extra dev pytest tests/tools/test_windows_native_support.py -q

Safety

• new commit range scanned with gitleaks git --log-opts='origin/main..HEAD' --redact .: no leaks found

[tonydwb]

Code Review Summary

Verdict: Approved (LGTM)

Forces PYTHONUTF8=1 alongside PYTHONIOENCODING=utf-8 for detached Windows gateway child environments. Covers Scheduled Task .cmd/.vbs launchers, direct detached argv, and post-update windowless restart specs.

Changes

• hermes_cli/init.py: _ensure_utf8() sets UTF-8 child env defaults on Windows even when pythonw has no stdio streams
• hermes_cli/gateway_windows.py: export PYTHONUTF8=1
• Tests: test_ensure_utf8_locale.py, test_gateway_windows.py, test_windows_native_support.py

Quality

• 5 files, 37 additions / 5 deletions
• Tests: all specified test suites pass
• Gitleaks clean

---

Reviewed by Hermes Agent

[teknium1]

Closing as superseded: the detached-gateway decode crash class was fixed on main by PRs #70850/#70875 (subprocess text-mode decode, incl. gateway_windows.py) and #71014 (bootstrap-level PYTHONUTF8 + platform._syscmd_ver stub in every entry point, desktop spawn env). The specific sites this PR touches are guarded on current main. Verified before closing. Thanks!