feat: Phase 4 — reusable "subscribe" workflow (+ dogfood it) (#8)

Centralizes the consumer stub into a reusable Gitea workflow
(.gitea/workflows/review-reusable.yml, workflow_call + defaulted inputs +
secrets: inherit); gadfly's own dogfood is now a thin caller of it, which
proved end-to-end that github.event context propagates into the reusable
on this act_runner. Adds the slim examples/reusable.yml stub + docs.

Folded in the swarm's findings: timeout_minutes default 30->45, map
GADFLY_API_KEY, explicit permissions block, drop the dead specialist_suite
input, and harden the example's actor gate. ~70 findings graded.

Completes the gadfly-games build (Phases 1-4 + quality fixes).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Steve Dudenhoeffer <steve@stevedudenhoeffer.com>
Co-committed-by: Steve Dudenhoeffer <steve@stevedudenhoeffer.com>

README.md

@@ -37,9 +37,12 @@ Gadfly ships as a container image, so consuming repos don't build anything — t
 it. Drop one file in your repo and set a couple of secrets/vars:
 
 1. Copy a stub from [`examples/`](examples/) to `.gitea/workflows/adversarial-review.yml` in
-   your repo — [`adversarial-review.yml`](examples/adversarial-review.yml) for the Ollama Cloud
-   default, or a provider-specific one (local Ollama, OpenAI-compatible, endpoint aliases). See
-   the [examples index](examples/README.md).
+   your repo. Two flavors: the slim [`reusable.yml`](examples/reusable.yml) — a tiny caller of
+   Gadfly's **reusable workflow** (`uses: steve/gadfly/.gitea/workflows/review-reusable.yml@…`
+   + `secrets: inherit`), best when you take the defaults — or the full self-contained
+   [`adversarial-review.yml`](examples/adversarial-review.yml) (Ollama Cloud default, with inline
+   notes for every provider / local Ollama / OpenAI-compatible / endpoint aliases). See the
+   [examples index](examples/README.md).
 2. Add repo config:
    - **secret** `OLLAMA_CLOUD_API_KEY` — your [Ollama Cloud](https://ollama.com) key (empty
      ⇒ Gadfly posts a harmless "not configured" notice instead of reviewing). *Not needed if