fix: allocate hidden console for detached server
Starting the server with UV_PROCESS_DETACHED results in DETACHED_PROCESS, leaving the child without a console. Without a console:
CONIN$ / CONOUT$ cannot resolve, causing channel_from_stdio to fail.
ConPTY cannot attach, breaking :terminal.
This patch allocates a hidden console via AllocConsole() when the server has none, restoring working stdio and enabling ConPTY.
Also updates os_set_cloexec to clear HANDLE_FLAG_INHERIT on the RPC pipe
handles, matching the Unix F_DUPFD_CLOEXEC behavior.
b40ca5a01c