429 (Too Many Requests) was incorrectly classified as context overflow,
triggering compaction instead of retry with backoff. The original logic
assumed token-based rate limiting correlates with context overflow, but
these are different concepts:
- Rate limiting (429): requests/tokens per time period (throughput)
- Context overflow: single request exceeds context window (size)
Now 429 errors are handled by the existing retry logic with exponential
backoff, while 400/413 remain as potential context overflow indicators.
fixes#1038
25707f9ad4