v0.98.9

Added

• Opt-in stale-recipient warning (synapse hub --warn-stale-recipients): a directed message to a
  recipient that is present but not proven wake-capable — no live -rx waiter sidecar and no
  genuine reaction within --recipient-liveness-window seconds (default 90) — draws a private
  recipient_liveness_warning back to the sender, so a reply that never comes is surfaced instead
  of silently waited on. Off by default, so an open hub tracks no reactions and warns nobody; the
  message is still delivered and journalled unchanged. Closes the "online but deaf agent"
  coordination gap where presence outlived liveness.
• synapse who roster liveness (same opt-in): a present-but-deaf agent is marked (deaf …), and a
  trailing Unarmed (present, no live waiter) line names the agents an operator should re-arm. The
  who snapshot carries an additive agent_liveness field when the warning is on.
• Waiter liveness now requires a live sidecar, not merely a present one: a -rx socket counts as a
  waiter only while its keepalive is fresh within --waiter-liveness-window seconds (default 20), so
  a hung or exiting waiter no longer vouches for its agent. A synapse-arm@ systemd unit
  (synapse init --install-user-services, Restart=always) is the documented self-healing waiter
  path; docs/recipes.md covers it.