fix(file-tools): normalize MSYS paths to prevent Windows ghost tree writes

[CodeForgeNet]

What does this PR do?

Normalizes MSYS paths passed to file tools (write_file and patch) on Windows. Previously, paths like /c/Users/... were interpreted literally, causing successful writes to land in ghost trees (e.g., C:\c\Users\...) instead of the actual directory. This ensures Windows path resolution matches the terminal backend behavior.

Related Issue

Fixes #46876

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🛡️ Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)

[alt-glitch]

Duplicate of #44735 — both PRs fix the same Windows MSYS path-resolution bug (#46876) by adding _normalize_msys_path to tools/file_tools.py, translating /c/Users/... to C:\Users\... so writes don't land in the C:\c\Users\... ghost tree. #44735 (open, filed 3 days earlier) is the canonical version and is more complete — it also handles /cygdrive/ and /mnt/ prefixes and patches the path-resolution warning path.

This PR's extra value (wiring the normalization into _sentinel_free_abs_cwd for TERMINAL_CWD and the broader test coverage) is worth folding into #44735. Related: closed predecessor #44765 (same approach), tracking issue #46876.