[i18n] Proposal: Simplified Chinese translation for the Context Course

## Proposal

I’d like to propose a Simplified Chinese localization of the Context Course.

I checked the current issues and pull requests and did not find an existing Chinese translation effort. To keep the initial scope small, I would start with Unit 0 only (`units/en/unit0/introduction.mdx`) and a minimal translated table of contents.

I would not begin the remaining units until the maintainers have reviewed the pilot and confirmed the preferred workflow.

## Translation approach

- Preserve code blocks, commands, URLs, filenames, product names, and API identifiers.
- Translate and manually review the explanatory prose.
- Maintain a small terminology glossary for recurring terms such as “skill”, “context engineering”, “MCP”, “plugin”, “subagent”, and “hook”.
- Build and preview the translated documentation before opening a PR.
- Submit later units as separate, reviewable PRs.

## Questions

1. Is a Simplified Chinese localization welcome at this stage?
2. Which locale code and directory name should be used: `zh-CN`, `zh-Hans`, or another convention?
3. Should a partial translation contain only the translated entries in `_toctree.yml`?
4. Are any workflow or documentation-build changes required to publish an additional language?
5. Is one unit per PR the preferred review size?
6. Should code comments and text embedded in images be translated, or remain in English?

If this direction is acceptable, I can prepare Unit 0 as a pilot and revise the plan based on maintainer feedback.

Start with units/en/unit0/introduction.mdx and the minimal translated _toctree.yml entry. First resolve the locale, directory, partial-toctree, workflow, and translation-scope questions with maintainers. Done means Unit 0 prose is translated and reviewed while code blocks, commands, URLs, filenames, product names, and API identifiers are preserved, with the documentation build previewed.

Written by the indexing model from the issue text.