ci: add Gitea Actions workflow and Docker Compose test runner; add test image\n\ngovernance: encode CI/containers rules in system prompts and AGENTS templates; update proposal and docs

docker/compose.yml

@@ -0,0 +1,19 @@
+name: codexhelper
+
+services:
+  tests:
+    build:
+      context: ..
+      dockerfile: docker/test/Dockerfile
+    container_name: codexhelper-tests
+    working_dir: /work
+    volumes:
+      - ..:/work:Z
+    command: ["/bin/bash", "-lc", "scripts/test.sh"]
+    networks:
+      - codexhelper-net
+
+networks:
+  codexhelper-net:
+    name: codexhelper-net
+