feat: implement proxy configuration and mode handling in CLI

[yaonyan]

This pull request introduces a new proxy mode to the MCPC CLI, allowing users to easily wrap and orchestrate existing MCP servers with minimal configuration. It also adds support for overriding agent execution modes via a CLI flag, improves plugin extensibility by automatically injecting a code execution plugin, and updates documentation and examples to reflect these new capabilities.

Proxy mode and agent configuration enhancements:

• Added a --proxy CLI flag and supporting logic to generate an MCPC configuration that wraps an MCP server, with transport type selection and automatic agent naming based on the command. This is implemented in the new createProxyConfig function and integrated into argument parsing and config loading. [1] [2] [3] [4] [5] [6]
• Added support for a --mode CLI flag to override the execution mode for all agents, via the new applyModeOverride function and integration into config loading. [1] [2] [3] [4] [5] [6] [7]

Plugin extensibility:

• Automatically injects the @mcpc-tech/plugin-code-execution plugin into all agents during CLI and server startup, improving code execution capabilities out of the box. [1] [2] [3]

Documentation and usability improvements:

• Updated CLI help text, options, and example usage to reflect new proxy mode, transport types, and execution mode overrides. [1] [2] [3]

Testing:

• Added a test to verify proxy mode correctly parses and generates agent configuration from CLI arguments.