v0.18.9

Changed

• Lower memory footprint. With the freeze fixed (memory now
  oscillates in a bounded band), the caps were tightened to roughly halve
  the per-instance footprint and the per-parse transients, leaving more
  headroom: the viewer window is 4MB (was 8MB), the history cache keeps 4
  sessions (was 8), the tail re-parse window is 1MB/2MB (was 2MB/4MB), and
  discovery reads a 256KB prompt tail (was 1MB). Measured on a 104MB
  session, the viewer parse transient dropped from ~40MB to ~18MB and its
  retained set from ~17MB to ~7MB. The viewer's scrollback is now the
  recent ~4MB of a session; full history remains in report / summary.