Add a locale-aware tool description system that loads translations from
TOML files in tool_descriptions/. This enables non-English users to see
tool descriptions in their language.
- Add src/i18n.rs module with ToolDescriptions loader, locale detection
(ZEROCLAW_LOCALE, LANG, LC_ALL env vars), and English fallback chain
- Add locale config field to Config struct for explicit locale override
- Create tool_descriptions/en.toml with all 47 tool descriptions
- Create tool_descriptions/zh-CN.toml with Chinese translations
- Integrate with ToolsSection::build() and build_tool_instructions()
to resolve descriptions from locale files before hardcoded fallback
- Add PromptContext.tool_descriptions field for prompt-time resolution
- Add AgentBuilder.tool_descriptions() setter for Agent construction
- Include tool_descriptions/ in Cargo.toml package include list
- Add 8 unit tests covering locale loading, fallback chains, env
detection, and config override
Closes#3901
81d99f513c