Add context7.json and Context7 refresh workflow

[martyanovandrey]

Our docs are already indexed by Context7 as /diplodoc-platform/docs, but the index was created without any configuration from our side. This PR takes control of how the library is parsed.

context7.json

• Indexes only the en tree. Both languages carry the same code examples, so indexing ru as well doubled every snippet in the agent context. Three guides exist only in ru so far (multilingual-projects, pdf-styles, the supported-languages include); they will show up once translated.
• Excludes _assets, _images, .github and the repository README.
• Adds rules: short YFM guidelines that Context7 shows to coding agents next to the snippets (closed blocks, relative .md links, toc.yaml, multiline tables, what is not enabled by default, how to build).

Refresh workflow

.github/workflows/context7-refresh.yml calls the Context7 refresh API on every push to master, so the index follows the docs instead of waiting for the popularity-based schedule (45 days for our rank). It needs the CONTEXT7_API_KEY repository secret; until it is set the job fails harmlessly.

Follow-ups outside the repo: claim the library in the Context7 dashboard (adds url and public_key to this file) and trigger a manual refresh once this is merged so the new configuration applies.

[github-actions]

✅ Documentation build

Revision built successfully
Revision preview link

Build logs

Warnings (2)

⚠️ en/guides/openapi.md: 168: YFM001 / inline-code-length Inline code length [Expected: 100; Actual: 265] [Context: " — the specification is displayed directly on the page (default value). If the size of the specification's json schema exceeds the value of ##maxOpenapiIncludeSize## (100 KB by default), the mode automatically switches to "]

⚠️ en/tools/docs/build.md: 52: YFM001 / inline-code-length Inline code length [Expected: 100; Actual: 109] [Context: " — a snapshot of the dependency graph (pages, included files, assets, missing paths, edge count), as well as "]

[github-actions]

✅ Documentation build

Revision built successfully
Revision preview link

Build logs

Warnings (2)

⚠️ en/guides/openapi.md: 168: YFM001 / inline-code-length Inline code length [Expected: 100; Actual: 265] [Context: " — the specification is displayed directly on the page (default value). If the size of the specification's json schema exceeds the value of ##maxOpenapiIncludeSize## (100 KB by default), the mode automatically switches to "]

⚠️ en/tools/docs/build.md: 52: YFM001 / inline-code-length Inline code length [Expected: 100; Actual: 109] [Context: " — a snapshot of the dependency graph (pages, included files, assets, missing paths, edge count), as well as "]

[github-actions]

✅ Documentation build

Revision built successfully
Revision preview link

Build logs

Warnings (2)

⚠️ en/guides/openapi.md: 168: YFM001 / inline-code-length Inline code length [Expected: 100; Actual: 265] [Context: " — the specification is displayed directly on the page (default value). If the size of the specification's json schema exceeds the value of ##maxOpenapiIncludeSize## (100 KB by default), the mode automatically switches to "]

⚠️ en/tools/docs/build.md: 52: YFM001 / inline-code-length Inline code length [Expected: 100; Actual: 109] [Context: " — a snapshot of the dependency graph (pages, included files, assets, missing paths, edge count), as well as "]

[github-actions]

✅ Documentation build

Revision built successfully
Revision preview link

Build logs

Warnings (2)

⚠️ en/guides/openapi.md: 168: YFM001 / inline-code-length Inline code length [Expected: 100; Actual: 265] [Context: " — the specification is displayed directly on the page (default value). If the size of the specification's json schema exceeds the value of ##maxOpenapiIncludeSize## (100 KB by default), the mode automatically switches to "]

⚠️ en/tools/docs/build.md: 52: YFM001 / inline-code-length Inline code length [Expected: 100; Actual: 109] [Context: " — a snapshot of the dependency graph (pages, included files, assets, missing paths, edge count), as well as "]