Serbero v0.2.4

Changed

• A facts_gathered handoff now waits for both parties. In production,
  Serbero handed disputes to a solver minutes after the first party wrote,
  before the other had said anything (the seller's own statement, or the
  buyer's, was enough). The rows of the decision table that find the facts
  gathered now wait until both parties wrote at least once; the party who
  did is thanked, and the response timers (reminder, unresponsive)
  cover the silent one (docs/judgments.md §4). Validated guidance still
  follows the actor's own word and does not wait.
• Before the facts_gathered handoff, the session holds for a grace
  period so the parties can resolve the dispute themselves. A new
  [mediation].handoff_grace (default "30m") starts once both parties
  were heard: both get the new hold_notice template, which names no fund
  action, and the dispute is handed off only if it is not resolved in time.
  Resolved meanwhile, it closes as self-resolved and the parties get
  resolved_thanks. handoff_grace = "0s" restores the immediate handoff
  (docs/spec.md §7.6). The es and pt texts of hold_notice await a
  native speaker's review.