fix: harden Windows compatibility

[dlxeva]

Summary

• make init output safe in GBK PowerShell
• normalize Windows and Git Bash paths at CLI boundaries
• make current-state checks and tests portable across platforms
• add Windows Python 3.12 CI coverage
• preserve a sanitized observed Windows compatibility record

Verification

• 231 pytest tests passed locally
• forced repository source-tree smoke passed
• current-state freshness check passed
• workflow YAML parsed successfully
• git diff check passed

Validation boundary

This remains a Draft PR. GitHub Windows CI and a real Windows host rerun are required before merge or release.