docs: add iFlow Search LangChain JS tools

[lzy (zhengyanglsun)]

Adds a JS-only integration page for @iflow-ai/search-langchain (community-maintained, third-party, currently pre-1.0 / @next) and a single Card entry on the JS tools index.

Scope (minimal, 2 files):

• New: src/oss/javascript/integrations/tools/iflow_search.mdx
• Modified: src/oss/javascript/integrations/tools/index.mdx — one Card added alphabetically (between Google Routes Tool and JigsawStack Tool).

Not touched: src/docs.json, packages.yml, providers pages, Python docs.

Page covers: install (npm/yarn/pnpm including @next), credentials via IFLOW_API_KEY env var (placeholder only — no real key), security-boundary note, instantiation of the three tool factories (createIFlowWebSearchTool, createIFlowImageSearchTool, createIFlowWebFetchTool) plus the convenience createIFlowSearchTools, direct .invoke() example, and createReactAgent example.

The package is explicitly framed as community-maintained and not part of LangChain core. Tracking issue: langchain-ai/langchainjs#10931. Source: https://github.com/zhengyanglsun/iflow-search-js.

Checks run locally: markdownlint clean on both files; git diff --check clean; secret-scan clean (no real keys, tokens, or tunnel URLs in the diff).

[github-actions]

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

• @npentrel or @lnhsingh (JavaScript integrations)

[lzy (zhengyanglsun)]

Status update — @iflow-ai/search-langchain@0.1.0 and @iflow-ai/search-core@0.1.0 have shipped to npm latest (verifiable with npm view @iflow-ai/search-langchain dist-tags and npm view @iflow-ai/search-core dist-tags).

The exported factory surface remains unchanged:

• createIFlowWebSearchTool
• createIFlowImageSearchTool
• createIFlowWebFetchTool
• createIFlowSearchTools

The tool names are also unchanged:

• iflow_web_search
• iflow_image_search
• iflow_web_fetch

This PR currently uses @next install snippets because it was opened during prerelease. Bare install now resolves to stable 0.1.0, so I’m happy to refresh the branch to simplify the install command to:

npm install @iflow-ai/search-langchain @iflow-ai/search-core @langchain/core

This remains a community / third-party integration; no implied LangChain endorsement.