feat: Remove OpenRouter support, replace litellm with Chutes API

[echobt]

Summary

This PR removes OpenRouter support and replaces litellm with direct Chutes API client using httpx.

Changes

• Remove OPENROUTER from Provider enum, add CHUTES
• Update get_api_key() to use CHUTES_API_KEY
• Update get_base_url() to use https://api.chutes.ai/v1
• Rewrite LLM client using httpx instead of litellm
• Update default model to deepseek/deepseek-chat
• Remove litellm from requirements.txt and pyproject.toml
• Update all documentation references
• Keep LiteLLMClient alias for backward compatibility

Breaking Changes

⚠️ litellm dependency removed - Projects relying on litellm features need to migrate.
⚠️ OpenRouter no longer supported - Use Chutes API instead.

Migration

# Before
export OPENROUTER_API_KEY="sk-or-..."

# After
export CHUTES_API_KEY="cpk_..."

Testing

python3 -c "from src.llm.client import LLMClient; print('OK')"

Related

• Part of umbrella PR for Chutes API complete integration
• 🔗 Depends on: feat: Integrate Chutes API with Kimi K2.5-TEE model #7 (Chutes API integration), docs: Comprehensive documentation with Mermaid diagrams #8 (Documentation)
• 🔗 Final step before umbrella merge

[coderabbitai]

Warning

Rate limit exceeded

@echobt has exceeded the limit for the number of commits that can be reviewed per hour. Please wait 29 minutes and 33 seconds before requesting another review.

⌛ How to resolve this issue?

After the wait time has elapsed, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

We recommend that you space out your commits to avoid hitting the rate limit.

🚦 How do rate limits work?

CodeRabbit enforces hourly rate limits for each developer per organization.

Our paid plans have higher rate limits than the trial, open-source and free plans. In all cases, we re-allow further reviews after a brief timeout.

Please see our FAQ for further information.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feature/remove-openrouter-litellm

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[echobt]

Part of Umbrella PR: #6 (Epic: Complete Chutes API Integration)

This PR is the final step in the stacked PR sequence:

1. feat: Integrate Chutes API with Kimi K2.5-TEE model #7 - Chutes API integration (merge first)
2. docs: Comprehensive documentation with Mermaid diagrams #8 - Documentation (depends on feat: Integrate Chutes API with Kimi K2.5-TEE model #7)
3. This PR (feat: Remove OpenRouter support, replace litellm with Chutes API #9) - OpenRouter removal (depends on feat: Integrate Chutes API with Kimi K2.5-TEE model #7 and docs: Comprehensive documentation with Mermaid diagrams #8)

Note: After #7 and #8 are merged, this PR should be rebased on main before merging.

Please see #6 for the complete merge strategy.