Scope CI/CD to build+test only; clean up runner infra

Remove automated deploy — Portainer handles deployments for now.
build.yml: deploy job removed, only builds and pushes image to registry.
infra/runner-compose.yml: clean standalone Portainer stack for act_runner,
  no swarm network dependency, uses external Forgejo URL.
infra/runner-swarm.yml: removed (replaced by runner-compose.yml).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

infra/runner-compose.yml

@@ -0,0 +1,25 @@
+# Forgejo Actions runner — deploy as a standalone Portainer stack.
+# The runner connects outbound to Forgejo to receive jobs; no inbound ports needed.
+# /var/run/docker.sock is mounted so the build job can run Docker Buildx.
+#
+# Setup: see the walkthrough at infra/RUNNER_SETUP.md
+
+services:
+  act_runner:
+    image: gitea/act_runner:latest
+    restart: unless-stopped
+    environment:
+      - GITEA_INSTANCE_URL=https://git.fabledsword.com
+      - GITEA_RUNNER_REGISTRATION_TOKEN=${RUNNER_TOKEN}
+      - GITEA_RUNNER_NAME=swarm-runner
+      # Maps the runs-on: ubuntu-latest label used in workflow files to a Docker image.
+      - GITEA_RUNNER_LABELS=ubuntu-latest:docker://node:20-bullseye
+      - CONFIG_FILE=/config/config.yml
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+      - act_runner_data:/data
+      - /nfs/data/fabledsword/act_runner/config.yml:/config/config.yml:ro
+    # No network needed — runner only makes outbound HTTPS connections to Forgejo.
+
+volumes:
+  act_runner_data: