Windows support (localhost TCP fallback)

[amaar-mc]

Wit currently uses Unix domain sockets for daemon communication. Windows doesn't support Unix sockets natively.

The plan (already in the design):

• Fallback to localhost:7337 TCP on Windows
• Detect platform in shared/paths.ts and choose socket vs TCP
• Update client.ts fetch calls to use TCP URL on Windows
• Update daemon/index.ts to bind to TCP port on Windows
• Tests on Windows CI

The architecture already accounts for this — it's a matter of implementing the fallback path.