docs: sync project guides to the new CI flow

Aligns the project guides with the branching/CI/environment changes
landed in the previous commits:

- CLAUDE.md: per-stage CI gate now closes against gitea.lan; describes
  the main/development/feature/* flow and the workflow surface
- docs/ARCHITECTURE.md: new section 18 "CI and Environments" covering
  branches, workflows, and the local-dev / dev-deploy / local-ci
  triad; section numbering shifted accordingly
- tools/local-ci/README.md: marked as fallback (offline / runner
  isolation only)
- tools/local-dev/README.md and ui/README.md: cross-link to
  tools/dev-deploy/ for production-shaped testing

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/ARCHITECTURE.md

@@ -751,7 +751,50 @@ addition.
   `GET /readyz` (Postgres reachable, migrations applied, gRPC listener
   bound). Probes are excluded from anti-replay and rate limiting.
 
-## 18. Deployment Topology (informational)
+## 18. CI and Environments
+
+The repository is monorepo and intentionally so — semver tags and
+per-service rollouts are achievable without splitting the code into
+multiple repositories.
+
+Branches:
+
+- `main` — production-track. Direct pushes are disallowed; the only
+  way in is a PR merge from `development`.
+- `development` — long-lived dev integration branch. Every merge
+  triggers an auto-deploy into the long-lived dev environment on the
+  CI host, reachable through the host Caddy at
+  `https://www.galaxy.lan` and `https://api.galaxy.lan`.
+- `feature/*` — short-lived branches off `development`. Merged back
+  via PR; PRs run unit + integration checks before merge.
+
+Workflows under `.gitea/workflows/`:
+
+| File | Trigger | Purpose |
+|------|---------|---------|
+| `go-unit.yaml` | push + PR matching Go paths | Fast Go unit tests. |
+| `ui-test.yaml` | push + PR matching `ui/**` | Vitest + Playwright. |
+| `integration.yaml` | PR to `development` / `main`; push to `development` | testcontainers integration suite. |
+| `dev-deploy.yaml` | push to `development` | Build images, seed UI volume, `compose up` against `tools/dev-deploy/`. |
+| `prod-build.yaml` | push to `main` | Build production images and persist `docker save` bundles as artifacts. |
+| `deploy-prod.yaml` | manual `workflow_dispatch` | Placeholder for the future SSH-based production rollout. |
+
+Environments:
+
+- **`tools/local-dev/`** — single-developer playground. Bound to
+  host ports, Vite dev server runs on the host. Not driven by CI.
+- **`tools/dev-deploy/`** — long-lived dev environment behind
+  `*.galaxy.lan`, redeployed on every merge into `development`.
+- **production** — future. Images come from the
+  `galaxy-images-commit-<sha>` artifact produced by `prod-build.yaml`
+  and are shipped to the production host via `docker save` →
+  `ssh prod docker load` → `docker compose up -d`.
+
+`tools/local-ci/` remains as an opt-in fallback runner for testing
+workflow changes without `gitea.lan`. It is no longer part of the
+per-stage CI gate; see `CLAUDE.md` for the gate definition.
+
+## 19. Deployment Topology (informational)
 
 - MVP runs three executables: one `gateway` instance, one `backend`
   instance, and N `galaxy-game-{game_id}` containers managed by backend.
@@ -770,7 +813,7 @@ Future scale-out hooks (not in MVP):
 - mTLS between gateway and backend.
 - Docker-socket-proxy sidecar fronting Docker daemon access.
 
-## 19. Glossary
+## 20. Glossary
 
 - **device_session_id** — opaque identifier of an authenticated client
   device; primary key of the device session record.