(docs) add KServe chat integration docs for Python and JavaScript

[Marton Schneider (schneidermr)]

Overview

Add new KServe integration docs for both Python and JavaScript/TypeScript chat models, including setup, instantiation, invocation, streaming, tool calling, structured output, vision input, and protocol behavior. Also add discoverability updates in integration index pages and route aliases in src/docs.json.

Type of change

Type: New documentation page

Checklist

• I have read the contributing guidelines, including the language policy
• I have tested my changes locally using docs dev
• All code examples have been tested and work correctly
• I have used root relative paths for internal links
• I have updated navigation in src/docs.json

Additional notes

Added pages:

• src/oss/python/integrations/chat/kserve.mdx
• src/oss/javascript/integrations/chat/kserve.mdx

Updated index pages:

• src/oss/python/integrations/chat/index.mdx
• src/oss/javascript/integrations/chat/index.mdx

Added docs.json aliases for langchain-kserve URL variants to canonical /kserve routes.

[github-actions]

❌ Import check failed

This PR contains imports from langchain_core that should be imported from langchain instead.

Detailed issues

Analyzing diff for import issues...
 Found 2 import issues:

File: src/oss/python/integrations/chat/kserve.mdx
Line: 109
Issue: Import from langchain.tools instead of langchain_core.tools
Current:   from langchain_core.tools import tool
Suggested: from langchain.tools import tool
--------------------------------------------------------------------------------
File: src/oss/python/integrations/chat/kserve.mdx
Line: 140
Issue: Import from langchain.messages instead of langchain_core.messages
Current:   from langchain_core.messages import HumanMessage
Suggested: from langchain.messages import HumanMessage
--------------------------------------------------------------------------------

 Found 2 import issues that need to be fixed.

Why this is a problem

The langchain package re-exports many modules and classes from langchain_core. When possible, imports should use langchain instead of langchain_core for:

• Better user experience (single import source)
• Consistency across documentation
• Reduced cognitive load for users

How to fix

Replace the imports as suggested above. For example:

• ❌ from langchain_core.messages import HumanMessage
• ✅ from langchain.messages import HumanMessage

🤖 Automated check

This check is based on the latest analysis of langchain re-exports from langchain_core.