Fixes#2043. On Git Bash for Windows, Claude Code hands script paths to
the shim in POSIX form (`/c/Users/...`). We exec a Windows `python.exe`
(the `python3` Microsoft Store stub fails the probe), and Windows Python
interprets the leading `/` as the root of the current drive — `/c/...`
becomes `C:\c\Users\...` or `D:\c\Users\...` depending on which
drive the shell happens to be on, fails with ENOENT, and every
Edit/Write/MultiEdit blocks until the session restarts.
Convert absolute path args via `cygpath -w` (a Git Bash builtin) before
exec. Guarded by `command -v cygpath` so macOS/Linux fall straight
through unchanged; `cygpath -w` is idempotent on already-Windows paths
so the rare mixed-form case is safe. Only `/*` paths are converted —
Windows-form paths reaching the shim are already openable by python.exe.
Verified locally:
- cygpath absent on macOS → guard skips → POSIX behavior unchanged
- end-to-end shim invocation with a POSIX path on macOS exits 0
- stubbed cygpath -w on /c/Users/test/hook.py produces C:\Users\test\hook.py
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
