Summary

Adds OpenRouter as a fully supported LLM provider for both LLM Proxy and Chat.

Closes #1929

Changes

• Added OpenRouter LLM Proxy routes (/v1/openrouter/{agentId}/chat/completions)
• Added OpenRouter support in Chat UI with model selection
• Added OpenRouter API key management in settings
• Updated documentation for supported providers
• Added e2e tests for OpenRouter integration

Demo Videos

• Non-streaming (Postman): Screencast from 2026-01-09 00-42-27.webm

• Streaming (Chat UI): Screencast from 2026-01-09 00-43-47.webm

API Key Instructions

Get your OpenRouter API key from: https://openrouter.ai/keys

Checklist

• Non-streaming responses work correctly
• Streaming responses work correctly
• Tool invocation and persistence
• Token/cost limits
• Model optimization
• Tool results compression
• Chat conversations work
• Model listing and selection
• Error handling
• Documentation updated
• E2E tests added

/claim #1929