v0.18.8

Fixed

• Per-file caches no longer leak over long runs. The discovery caches
  (model/liveState, row title, entrypoint, sub-agent info) were keyed by
  path:mtime with no eviction, so an actively-appending session added a
  new entry every ~2s poll and never dropped the old one — a slow leak
  that bloated memory over a multi-hour watch. They're now keyed by path
  (mtime stored in the value), so a changed file overwrites its single
  entry: one entry per file, bounded regardless of runtime. Rounds out
  the v0.18.5–0.18.7 freeze fixes.