fix: smart retry classification, Bedrock 200K context cap, batch error details

- retry.ts: respect isRetryable:false and 4xx status in JSON error bodies (Issue #7)
- provider.ts: cap Bedrock Anthropic models at 200K context (Issue #4)
- batch.ts: include per-tool error details in failure output (Issue #9)
- retry.test.ts: 5 new tests for catch-all retry classification

Author: praxstack