Add CLAUDE.md documentation for plugin development guidance

[xterao]

Overview

This PR adds comprehensive documentation for Claude Code to assist with development on the doma-tools-for-intellij plugin.

Changes

• Added CLAUDE.md file with:
  • Essential build commands reference
  • Architecture overview of the plugin
  • Key components and their relationships
  • Development guidelines and best practices
  • Package structure and naming conventions

Motivation

Providing clear guidance for AI-assisted development will help maintain consistency and quality when using Claude Code to work on this IntelliJ plugin project.

Testing

• Documentation follows project standards
• All links and references are valid
• Build commands have been verified

Related Issues

N/A

Notes

The documentation covers:

• Custom language support (DomaSql)
• Navigation between DAO and SQL files
• Code analysis and validation
• IDE integration features
• Development workflow