Add reply message tools

[4geru]

Background

With the rapid evolution of AI Agents and workflow automation tools, there's an increasing demand for seamless integration between AI systems and messaging platforms.
Modern AI Agent platforms like Mastra, n8n, and other workflow automation tools are becoming more sophisticated and require the ability to interact with users through various channels.

Currently, the LINE Bot MCP Server only supports push and broadcast messaging, which are paid features in LINE's pricing model.
However, reply messages are free, making them a more cost-effective solution for AI Agent interactions. Additionally, reply functionality enables immediate responses to user messages through webhook events, creating more natural conversational experiences.

Summary

This PR adds reply message functionality to the LINE Bot MCP Server, enabling webhook-based message responses that AI Agents can utilize for cost-effective, real-time user interactions.

Changes

New Tools Added

• reply_text_message: Reply with simple text messages using a reply token
• reply_flex_message: Reply with highly customizable flex messages using a reply token

Technical Changes

• Added src/tools/replyTextMessage.ts and src/tools/replyFlexMessage.ts
• Added NO_REPLY_TOKEN_ERROR constant for error handling
• Updated src/index.ts to register new reply tools
• Both tools require a replyToken parameter for webhook-based responses

Documentation Updates

• Updated README.md and README.ja.md to include new reply tools
• Renumbered existing tools (3-12) to accommodate new additions
• Added clear descriptions and input parameters for reply functionality

Use Case

These reply tools enable AI Agents to:

• Respond to user messages immediately using webhook events
• Utilize free reply messaging instead of paid push/broadcast features
• Integrate with modern workflow automation platforms (Mastra, n8n, etc.)
• Create more natural, cost-effective conversational experiences