v0.1.2

Adds a pipe-based 'process session kind alongside 'pty: a stream session over the child's stdin/stdout PIPES instead of a pseudo-terminal. This is the transport a tmux control-mode (tmux -C) client needs, since it hard-fails on a tty. Rides sigil 0.17.19's non-blocking pipe primitives. Denied without an exec grant (same as pty), write round-trips bidirectionally, resize is a no-op, session-close reaps the child. Existing sessions build unchanged.