feat: MCP session init and tool calls

[dwmkerr]

Summary

Add commands to initialize MCP sessions and call MCP tools directly from the terminal-ai CLI.

Use Case

When testing MCP servers (like shellwright), it's useful to manually call tools from the command line:

# Initialize session
tai mcp init http://localhost:7498/mcp

# Call a tool
tai mcp call shell_start '{"command":"bash"}'

This would simplify debugging and testing MCP integrations without needing a full MCP client.

Related

• shellwright has manual scripts for this: scripts/mcp-init.sh and scripts/mcp-tool-call.sh