--socket forwards -L verbatim when given; when OMITTED the CLI sends
no -L at all and agent-send.sh's own resolution governs (explicit -L >
MOSAIC_TMUX_SOCKET > unique hit > ambiguity refusal, B1/PR #1466).
Measured design note: comms.ts was already correct by construction
after B1 — this change pins it with a spec arm (no -L forwarded when
--socket omitted) and makes the contract explicit in the option help,
so a future default-guess here cannot silently reintroduce the
stale-twin defect. Specs 7/7.
marcie
