feat: add get_weather MCP tool using wttr.in API

- New agent/weather_mcp.py: stdio MCP server with get_weather(location)
  that returns a short conversational summary (temp, conditions, high/low)
- Register weather toolset in build_mcp_toolsets() alongside web-access
- Update system prompt with Weather section

agent/voice_agent.egg-info/SOURCES.txt

@@ -0,0 +1,6 @@
+pyproject.toml
+voice_agent.egg-info/PKG-INFO
+voice_agent.egg-info/SOURCES.txt
+voice_agent.egg-info/dependency_links.txt
+voice_agent.egg-info/requires.txt
+voice_agent.egg-info/top_level.txt