Adds a Context Overflow Errors subsection to custom-provider.md showing how a custom provider extension can rewrite unrecognized overflow errors via a message_end handler so pi's native compact-and-retry path triggers. Includes guard rails for provider scoping, idempotency, and avoiding rate-limit phrases.
- Document stream.push/end pattern instead of yield
- Link to existing provider implementations on GitHub
- Add testing section with list of test files to run
- Include proper content block and tool call examples
- Add resetApiProviders() to clear and re-register built-in providers
- Add createAssistantMessageEventStream() factory for extensions
- Add streamSimple support in ProviderConfig for custom API implementations
- Call resetApiProviders() on /reload to clean up extension providers
- Add custom-provider.md documentation
- Add custom-provider.ts example with full Anthropic implementation
- Update extensions.md with streamSimple config option
