feat: add claude-code-router support for multi-model testing

- Add ROUTER=true flag to route requests through claude-code-router
- Add router service to docker-compose with profile-based activation
- Support OpenAI (gpt-4o) and Google Gemini (gemini-2.5-pro) as alternatives
- Add router-config.json with provider configuration template
- Update .env.example with provider API key options
- Document router mode limitations (cost tracking shows $0)

docker-compose.yml

@@ -20,6 +20,8 @@ services:
     environment:
       - TEMPORAL_ADDRESS=temporal:7233
       - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY:-}
+      - ANTHROPIC_BASE_URL=${ANTHROPIC_BASE_URL:-}  # Optional: route through claude-code-router
+      - ANTHROPIC_AUTH_TOKEN=${ANTHROPIC_AUTH_TOKEN:-}  # Auth token for router
       - CLAUDE_CODE_OAUTH_TOKEN=${CLAUDE_CODE_OAUTH_TOKEN:-}
       - CLAUDE_CODE_MAX_OUTPUT_TOKENS=${CLAUDE_CODE_MAX_OUTPUT_TOKENS:-64000}
     depends_on:
@@ -36,5 +38,33 @@ services:
     security_opt:
       - seccomp:unconfined
 
+  # Optional: claude-code-router for multi-model support
+  # Start with: ROUTER=true ./shannon start ...
+  router:
+    image: node:20-slim
+    profiles: ["router"]  # Only starts when explicitly requested
+    command: >
+      sh -c "apt-get update && apt-get install -y gettext-base &&
+             npm install -g @musistudio/claude-code-router &&
+             mkdir -p /root/.claude-code-router &&
+             envsubst < /config/router-config.json > /root/.claude-code-router/config.json &&
+             ccr start"
+    ports:
+      - "3456:3456"
+    volumes:
+      - ./configs/router-config.json:/config/router-config.json:ro
+    environment:
+      - HOST=0.0.0.0
+      - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY:-}
+      - OPENAI_API_KEY=${OPENAI_API_KEY:-}
+      - GEMINI_API_KEY=${GEMINI_API_KEY:-}
+      - ROUTER_DEFAULT=${ROUTER_DEFAULT:-openai,gpt-4o}
+    healthcheck:
+      test: ["CMD", "node", "-e", "require('http').get('http://localhost:3456/health', r => process.exit(r.statusCode === 200 ? 0 : 1)).on('error', () => process.exit(1))"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 30s
+
 volumes:
   temporal-data: