v0.18.4

Fixed

• Finished sub-agents no longer show [waiting]. A sub-agent that
  produced its result and terminated ended its tail with a text-only
  turn, which the liveness classifier read as "waiting" — a verdict that
  only makes sense for an interactive top-level session. Sub-agents are
  one-shot, so a yielded turn now reads as done (the time-based badge),
  while a pending tool call still reads as [working].
• The tree selection no longer vanishes. When the selected session
  cooled and folded under the ... N cold row it dropped out of the
  nav list, leaving "No session selected" and silent j/k. The cursor
  now snaps to the nearest visible ancestor (sub-agent → session →
  project) whenever its row disappears, so navigation never freezes.