flaky test: `TestBatcherAutoDA`

CircleCI Insights reports 12 flakes across `go-tests-short` and `go-tests-full` in the current 14-day window (checked 2026-08-11).

CI runs:
- https://circleci.com/gh/ethereum-optimism/optimism/5437882
- https://circleci.com/gh/ethereum-optimism/optimism/5441048

Representative failure:

```
eip4844_test.go:290: L1 fees are: baseFee(1180), tip(1), blobBaseFee(45768). feeRatio: 38.753599
eip4844_test.go:323: "38.75359864521592" is not greater than "41"
expected feeRatio to be greater than 41 (calldata should be cheaper, even with Pectra)
--- FAIL: TestBatcherAutoDA (17.59s)
```

The retry passed in 27.84s on the same job.

Start with eip4844_test.go around the TestBatcherAutoDA failure at lines 290 and 323, then reproduce it through the go-tests-short and go-tests-full CI runs. Trace why the feeRatio sometimes falls below 41, and consider the issue done when the test no longer flakes while preserving the stated calldata-versus-blob fee expectation.

Written by the indexing model from the issue text.