Add Agent Mode with add/remove/list/mode commands

[a6b8]

Summary

Introduce Agent Mode as the default CLI mode with dedicated commands for tool management.

Changes

• New commands: search, add, remove, list, mode, helpAgent
• Mode system: agent (default) vs development
• index.mjs refactored into runAgentCommands() and runDevCommands()
• Config constants MODE_AGENT, MODE_DEVELOPMENT, agentCommands in config.mjs
• Agent-aware run, callTool, callListTools methods
• Local tool schema save/remove (#saveToolSchema, #removeToolSchema)
• #resolveMode, #resolveAgentSchemas, #extractParameters helpers