feat: live status-board comment — per-model/per-lens review progress

Phase 3 of the gadfly-games build. With several models × several lenses
reviewing a PR, all you'd see mid-run is a row of "⏳ Reviewing…"
placeholders. Add ONE consolidated, live-updating status-board comment
that aggregates every model's per-lens progress (queued → running →
finished + verdict), so progress is visible at a glance and a watcher
can tell when the whole swarm is done.

- cmd/gadfly: opt-in statusWriter (GADFLY_STATUS_FILE) publishes this
  model's lenses to a JSON file, written atomically (temp+rename) as
  runSpecialists transitions each lens. Inert when unset — plain runs
  and tests are unaffected.
- scripts/status-board.sh: background renderer that polls the status
  dir and upserts one marker comment every GADFLY_STATUS_POLL_SECS
  (default 12s), caching the comment id to PATCH in place. Advisory and
  best-effort; the per-model findings comments are untouched.
- entrypoint.sh: pre-seeds every model as queued, launches the board,
  waits only on the review lanes, then signals .done for a final render.
  Default on; disable with GADFLY_STATUS_BOARD=0.
- Docs: README config table + "Live status board" section, example
  stub note, CLAUDE.md architecture map.

gofmt clean, go vet quiet, go build + go test -race green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

examples/adversarial-review.yml

@@ -65,6 +65,10 @@ jobs:
           #   GADFLY_PROVIDER_LENS_CONCURRENCY: "ollama-cloud=3,m1=1"
           # GADFLY_LENS_CONCURRENCY: ${{ vars.GADFLY_LENS_CONCURRENCY }}
           # GADFLY_PROVIDER_LENS_CONCURRENCY: ${{ vars.GADFLY_PROVIDER_LENS_CONCURRENCY }}
+          # Live status board (optional; ON by default): one consolidated comment
+          # showing every model's per-lens progress as it runs. Disable with
+          # GADFLY_STATUS_BOARD=0; tune the refresh with GADFLY_STATUS_POLL_SECS.
+          # GADFLY_STATUS_BOARD: ${{ vars.GADFLY_STATUS_BOARD }}
           # --- Models & providers (optional; default = Ollama Cloud) ----------
           # Gadfly is majordomo-powered, so it can target other backends. Set a
           # provider for bare model ids; point at a different endpoint with a