Bug: Agent Node lacks graceful shutdown for Browser processes #11

Description

The Agent Node does not currently handle SIGTERM signals, and its BrowserSkill does not provide a mechanism to cleanly close the underlying browser engine and persistent contexts on shutdown. This can lead to zombie chromium processes in containerized environments.

Tasks

• Implement SIGTERM handling in agent_node/main.py.
• Add shutdown() method to BrowserSkill to close the Playwright engine.
• Ensure AgentNode triggers skill cleanup on exit.