Windows support (Git Bash / PowerShell)

[ropdias]

Context

The script is Bash-only. On Windows there are two realistic paths:

• Git Bash / MSYS2 — ships GNU coreutils and bash 4+, so the script may largely
  work already. Unverified. Likely friction points: transcript path separators,
  $XDG_RUNTIME_DIR being unset (falls back to /tmp, which maps to the MSYS temp),
  and how the host CLI passes the command on Windows.
• PowerShell — no Bash; out of scope for a .sh script. WSL is the recommended
  route and already works (it's Linux).

Proposal

• Verify the script under Git Bash with a real Claude Code session on Windows.
• Document the verified setup (and recommend WSL as the smoother option).
• Fix any path/temp-dir issues found, guarded so they don't regress Linux.

Acceptance

• Documented, verified Git Bash setup, or a clear "use WSL" recommendation with the
  reasons.