CLI: punch mcp list/add/remove/test commands

[humancto]

Proposed Solution

punch mcp list              # List configured MCP servers and their status
punch mcp add gmail         # Interactive wizard to add an MCP server  
punch mcp remove gmail      # Remove an MCP server
punch mcp test gmail        # Test connection, run capability handshake, show tools
punch mcp tools             # List all discovered tools across all servers

punch mcp add should:

1. Show a list of popular servers (Gmail, GitHub, Slack, Notion, filesystem)
2. Auto-generate the punch.toml config entry
3. Handle credential setup (env vars, OAuth flow where applicable)
4. Test the connection before saving