[qdeslandes]

Summary

Replace the Claude Agent SDK and Anthropic SDK integrations with OpenRouter's Chat Completions API. Each phase (proposal, implementation, and commit message) can then use any model available on OpenRouter, instead of a fixed list of Claude models.

• --proposal-model and --impl-model take OpenRouter model IDs, and the new --commit-model selects the commit message model. bfoptimizer checks the IDs against OpenRouter's model list at startup, and needs OPENROUTER_API_KEY instead of Anthropic credentials.
• The tool loop that the Claude Agent SDK provided now runs in bfoptimizer, with the same file and shell tools and the same 100-response limit. Reasoning details are passed back between rounds.
• Transient API failures are retried, and Anthropic models still cache the conversation across tool rounds.
• Commit message requests now count toward the displayed cost.
• The anthropic and claude_agent_sdk packages are no longer needed: the transport only uses the Python standard library.

Related issue

None. bfoptimizer was limited to Claude models, and this change removes that limit.

Testing

• Ran a round of optimizations.
• Checked retries and timeouts against a local HTTP server, and the startup model check against the live OpenRouter model list.

AI disclosure

Deferred most of the work to Claude, reviewed and owned by me

Checklist

• I understand every line in this PR and can explain why it is correct
• I built the project and ran the tests covering this change
• make -C $BUILD test_bin test passes and the code follows the style guide
• Commits are formatted as component: subcomponent: short description
• I have disclosed any AI usage above