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>

README.md

@@ -192,6 +192,30 @@ GADFLY_PROVIDER_LENS_CONCURRENCY: "ollama-cloud=3,m1=1"
 GADFLY_SPECIALISTS: "security,correctness,error-handling"
 ```
 
+### Live status board
+
+When several models (each with several lenses) review a PR, the individual findings land in
+**one comment per model** — but while that's in flight all you'd see is a row of
+`⏳ Reviewing…` placeholders. So Gadfly also upserts **one consolidated status-board comment**
+that aggregates every model's per-lens progress as it happens:
+
+```
+## 🪰 Gadfly — live review status
+1/3 reviewers finished · updated 2026-06-27 18:14:56Z
+
+#### `glm-5.2:cloud` · ollama-cloud — ⏳ 2/4 lenses
+- ✅ security — No material issues found
+- 🔄 correctness — running
+- ⏸️ performance — queued
+…
+```
+
+Each model process publishes its lenses (queued → running → finished + verdict) to a small
+JSON file, and a background renderer in `entrypoint.sh` re-renders + upserts the single comment
+every `GADFLY_STATUS_POLL_SECS` (default 12s) until the swarm finishes. It's advisory and
+best-effort — the per-model findings comments are unaffected — and entirely separate from those.
+Turn it off with `GADFLY_STATUS_BOARD=0`.
+
 ### Triggers
 
 1. A **new/reopened/ready** non-draft PR — automatic.
@@ -217,6 +241,7 @@ fixes. This keeps usage down.)
 ```
 cmd/gadfly/            the agentic reviewer binary (majordomo + Ollama Cloud); zero deps beyond stdlib + majordomo
 scripts/run.sh         fetches the PR diff, runs the reviewer, upserts one labeled comment
+scripts/status-board.sh    renders + upserts the single live status-board comment (per-lens progress)
 scripts/system-prompt.txt  the reviewer persona + verification discipline
 entrypoint.sh          the container brains: trigger gating, clone, model loop (logic lives here, not in YAML)
 Dockerfile             multi-stage; build-time module creds (BuildKit secrets) never reach the final image
@@ -252,6 +277,8 @@ The reviewer binary reads these (the stub/entrypoint set sane defaults):
 | `GADFLY_RECHECK` | on | set `0`/`false` to skip the recheck pass |
 | `GADFLY_RECHECK_MAX_STEPS` | 16 | recheck-pass step cap |
 | `GADFLY_MAX_DIFF_CHARS` | 60000 | diff chars embedded in the prompt (full diff via `get_diff`) |
+| `GADFLY_STATUS_BOARD` | on | set `0` to disable the live status-board comment |
+| `GADFLY_STATUS_POLL_SECS` | 12 | how often the status board re-renders/upserts |
 | `GADFLY_TRIGGER_PHRASE` | `@gadfly review` | comment phrase that re-triggers |
 | `GADFLY_ALLOWED_USERS` | *(collaborators)* | comma-separated allow-list for comment triggers |
 | `GADFLY_FINDINGS_URL` | — | gadfly-reports store base URL; set to enable findings telemetry (off when empty) |