docs: add Infino vector store integration (JavaScript)

[Ashish Mishra (ashishmishra26)]

Adds the JavaScript vector store integration docs for Infino, published as the independent package @infino-ai/langchain-infino.

Infino is an embedded retrieval engine that runs SQL, full-text (BM25), vector, and hybrid (RRF) search over a single copy of your data on object storage. InfinoVectorStore implements the standard LangChain VectorStore interface (addDocuments / delete / similaritySearch with structured metadata filtering, MMR, asRetriever) and additionally exposes hybrid + BM25 retrieval.

Per the integration contribution guide — independent package + a docs-only PR — this change only adds documentation:

• src/oss/javascript/integrations/vectorstores/infino.mdx — the integration guide (setup, instantiation, manage, query, filtering, hybrid/BM25, retriever).
• A card for Infino in index.mdx.

[github-actions]

Thanks for opening a docs PR, Ashish Mishra (@ashishmishra26)! When it's ready for review, please add the relevant reviewers:

• @npentrel or @lnhsingh (JavaScript integrations)

[langchain-automated-triage]

Thanks for contributing a new integration docs page, Ashish Mishra (@ashishmishra26)!

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[Ashish Mishra (ashishmishra26)]

cc Naomi Pentrel (@npentrel) Lauren Hirata Singh (@lnhsingh) — could one of you review when you have a chance? This adds the JavaScript vector store integration docs for the published @infino-ai/langchain-infino package (independent package per the contribution guide). Thanks!