fix(agent): cap figures + global region cap + reset active on stop

Three safety/robustness fixes from the operator's run logs:

- Cap figures per frame (MAX_FIGURES, default 8) like components/panels already
  are. Uncapped, a huge/busy image yielded hundreds of figure boxes → hundreds
  of per-figure CCIP calls + crops → a 38s job AND a submit too big to accept
  (image 81602 looped on 413). This is the acute fix.
- Global per-JOB backstop (MAX_REGIONS, default 128): if total regions still
  exceed the cap (long video), keep the highest-scoring and log the drop, so a
  submit body can never blow past curator's limit.
- Stale "active" meter: stop() now resets _active to 0 (no slots remain, so the
  meter must read 0 at once), and _bump clamps at 0 so a slot finishing after the
  reset can't drive it negative.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa

agent/fc_agent/app.py

@@ -15,7 +15,7 @@ from .worker import Worker
 # Bump on every agent change. The page embeds this and /status reports it; the UI
 # warns to reload when they differ — so a stale browser-cached page can't be
 # mistaken for "the new image didn't deploy". (Belt-and-braces with no-store.)
-VERSION = "2026-06-30.8 · ubuntu24.04-py312 · big-images"
+VERSION = "2026-06-30.9 · region-caps + active-reset"
 
 logbuf.install()
 cfg = Config.from_env()