docs(ai): knowledge-rag example declares adapterConfig, not the undeclared options key

`content/docs/ai/knowledge-rag.mdx` configured its `ragflow` knowledge source with
`options: { datasetId }`. `KnowledgeSourceSchema` declares `adapterConfig` and is a plain
`z.object` with no `.passthrough()`, so the key is dropped before any adapter sees it.
Since #19251 (card #18973, ruling batch #160 item 2, letter A) `extractRagflowOptions`
reads `source.adapterConfig` with no fallback, so a source copied from this page is
refused by name at the first upsert / search / delete:

    RAGFlow adapter requires source.adapterConfig.datasetId on source '<id>'

One line, one page. No spec change and no ADR-0087 conversion: `options` was never a key
`KnowledgeSourceSchema` accepted, so nothing an author could declare is removed.

Claude-Session: https://claude.ai/code/session_017ef78bLdybu3AffehKkhfk
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

content/docs/ai/knowledge-rag.mdx

@@ -34,7 +34,7 @@ kernel.use(new KnowledgeServicePlugin({
       label: 'Product docs',
       adapter: 'ragflow',
       source: { kind: 'http', urls: ['https://docs.example.com/sitemap.xml'] },
-      options: { datasetId: 'rgf_doc_dataset' },
+      adapterConfig: { datasetId: 'rgf_doc_dataset' },
     },
   ],
 }));