Mechanical `check_doc_links.py --fix` pass over website/docs (hand-authored
and generated pages) and the zh-Hans mirror: 1,868 route-style links
(`](/section/page#anchor)`, `](/docs/...)`) become `](../section/page.md#anchor)`.
Every target was asserted to exist on disk; anchors and query strings are
preserved; fenced code blocks and inline-code examples are untouched.
Two dead targets found by the converter were fixed by hand first:
memory-providers.md linked `/user-guide/plugins` (page is
`user-guide/features/plugins`), and the zh-Hans learning-path still linked the
removed `rl-training` page — ported the EN treatment (external Atropos link).
Docusaurus build after: EN locale 0 unresolved Markdown links, 0 broken links,
0 broken anchors.
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