文档补丁：英文主版 README + 中文双语版。
Docs patch: English primary README with a Chinese bilingual twin.
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README.md 重写为英文主版（Why 小节、安装、配置、存储、开发、claude-mem 对照）
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新增 README.zh.md 中文版与 README.i18n.yaml 双语一致性记录（沿用 DSH monorepo 惯例）
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修正「自包含」措辞、补充 DSH_CHECKOUT / DSH_CREDENTIALS 开发说明
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README.md rewritten as the English primary doc (Why, install, config, storage, dev, claude-mem comparison)
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New README.zh.md Chinese twin and README.i18n.yaml bilingual-pair record (DSH monorepo convention)
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Corrected the self-contained wording and added DSH_CHECKOUT / DSH_CREDENTIALS dev notes
代码无变化 / No code changes.