docs: CONTRIBUTING, AGENTS, CI, issue templates, and unit tests

[MisterBrookT]

Summary\n\n一次性补齐开源项目该有的基础设施：\n\n- CONTRIBUTING.md — dev setup、代码风格、commit 规范、PR checklist、项目结构说明\n- AGENTS.md — 给 AI coding agent（Claude Code / Copilot / Cursor）看的架构导读：数据模型、文件地图、如何加新 provider、常用命令、常见错误\n- CHANGELOG.md — 初始 v0.1.0 条目（commitizen 格式）\n- .env.example — 三个 API key 的模板，含链接\n- .github/workflows/ci.yml — Ruff lint + format check + pytest，跑 Python 3.10 / 3.11 / 3.12\n- .github/ISSUE_TEMPLATE/ — bug report + feature request（YAML 格式）\n- tests/ — 20 个单元测试，覆盖 VISItem 加载/保存/round-trip/业务逻辑，不需要任何 API key\n\n## Test plan\n\n- [ ] uv run pytest tests/ -v 本地全部通过\n- [ ] CI 三个 Python 版本全绿\n- [ ] AGENTS.md 内容准确反映当前代码结构"

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Generated by Claude Code

[gemini-code-assist]

Code Review

This pull request adds project configuration, documentation, and testing infrastructure for the IGenBench tool, including environment templates, GitHub issue templates, an AI agent guide, contributing guidelines, and unit tests for the VISItem data model. The review feedback points out unused imports (json, os, and pytest) in the newly added test file that should be removed to clean up the code.

Important

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[gemini-code-assist]

The imports json, os, and pytest are not used anywhere in this test file. Removing unused imports helps keep the codebase clean and adheres to PEP 8 style guidelines.

Suggested change

	import json
	import os
	from pathlib import Path
	import pytest
	from pathlib import Path

References

1. Unused imports should be removed to keep the namespace clean and adhere to PEP 8. ^(link)