Add IPC fallback for Warp notifications

[KRRT7]

Teach the Warp Claude Code plugin to prefer WARP_CLI_AGENT_IPC when present and fall back to /dev/tty otherwise. This keeps notifications working with newer Claude Code builds that no longer grant hooks terminal access.

[harryalbert]

nc -U ships with macOS but is not universally available on Linux (GNU netcat doesn't support -U). Since Claude Code is a Node.js app, node should be guaranteed on $PATH. Could we fall back to node when nc - U fails? Something like:

send_via_ipc() {
    (printf "%s" "$1" | nc -U "$WARP_CLI_AGENT_IPC") 2>/dev/null && return
    node -e "require('net').createConnection(process.argv[1]).end(process.argv[2])" \
        "$WARP_CLI_AGENT_IPC" "$1" 2>/dev/null || true
}

[KRRT7]

superseded by #52