- Use buildTextBlock for billing header to avoid raw JSON string interpolation
- Fix empty array edge case in prependToFirstUserMessage
- Allow remapOAuthToolNames to process messages even without tools array
- Move claude_system_prompt.go to helps/ per repo convention
- Export prompt constants (ClaudeCode* prefix) for cross-package access
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>