fix: Add dynamic Git detection; fix Windows 'command not found' and e…

[felix307253927]

…ncoding issues.

Summary

Changes

feat: add dynamic Git Bash path detection
fix: resolve Windows encoding/garbled text issues
fix: handle "command not found" errors on Windows
fix: ensure Git built-in commands are found when using Git Bash on Windows

Testing

• cargo clippy --workspace --all-targets -- -D warnings passes
• cargo test --workspace passes
• Live integration tested (if applicable)

Security

• No new unsafe code
• No secrets or API keys in diff
• User input validated at boundaries

[jaberjaber23]

Security regression in the safe path. The original code intentionally runs commands without shell interpretation (direct argv). This PR wraps ALL safe-path commands in cmd /C on Windows, which reintroduces shell interpretation (pipes, redirects, & all become live). This defeats the entire purpose of the safe path.

Other issues:

• Box::leak in get_git_sh_path() permanently leaks memory on every call. Use OnceLock or tokio::sync::OnceCell to compute and cache once.
• Missing std::os::windows::process::CommandExt import for creation_flags(CREATE_NO_WINDOW) — won't compile on Windows.
• PATH uses Unix colon separators but falls back to cmd.exe in some cases where semicolons are needed.

The cmd /C wrapping must be reverted from the safe path. The memory leak must be fixed. The missing import must be added.