Update documentation and examples for Claude Agent SDK and VOICEVOX

[74th]

This pull request introduces several improvements and refactorings to the documentation and sample applications, focusing on better organization, clearer instructions, and improved code structure for Claude Agent SDK and Gemini integration. The most important changes are summarized below.

Documentation improvements:

• Added a new comprehensive guide docs/create_your_claude_agent_sdk_apps.md for developing AI agent applications using Claude Agent SDK, including setup, workspace configuration, and server startup instructions.
• Updated docs/setup_ja.md and docs/run_sample_app_ja.md to clarify sample app execution, Docker usage for Voicevox, and to reference the new Claude Agent SDK guide. Also improved links and marked optional sections more clearly. [1] [2] [3] [4] [5] [6] [7] [8]

Claude Agent SDK sample refactor:

• Renamed example_apps/claude_agent_sdk/claude_agent_sdk.py to example_apps/claude_agent_sdk/app.py, removed unused tool/MCP server code, and simplified the client setup for clarity and maintainability. [1] [2] [3]

Gemini and echo sample improvements:

• Enhanced example_apps/gemini.py and example_apps/echo_with_move.py to include more expressive servo movements (listening, nodding, off poses) and robust handling of empty transcripts, improving user interaction. [1] [2] [3] [4]
• Removed redundant if __name__ == "__main__": blocks from sample apps, streamlining how they are executed. [1] [2] [3] [4]

Minor code and doc fixes:

• Adjusted the timing and placement of the "listening pose" servo movement in both documentation (README.md) and code to ensure consistency. [1] [2]

These changes collectively improve the developer experience, code maintainability, and documentation clarity for users building on this repository.