- Change all zai models from anthropic-messages to openai-completions API
- Update baseUrl from https://api.z.ai/api/anthropic to https://api.z.ai/api/coding/paas/v4
- Add compat setting to disable developer role for zai
- Update zai provider tests to use OpenAI-style options (reasoningEffort instead of thinkingEnabled/thinkingBudgetTokens)
- Enable previously disabled thinking and image input tests for zai models