flaky test: `TestELSyncSafeRetractedByOffset` — CrossSafe sync timeout during preset setup

**Claude:** Reporting a new flake.

## Flaky Test

`TestELSyncSafeRetractedByOffset` in `op-acceptance-tests/tests/sync/elsync/offset_el_safe/`

## CI Link

https://circleci.com/gh/ethereum-optimism/optimism/4907858

- Job: `memory-all-opn-op-geth` (CircleCI 4907858)
- Workflow: `main`
- Merge-queue pipeline for PR #20250, commit `c409fb370e462945e77526dd63afdaf87c4413c8`
- Test duration: 72.06s (of 940.43s total job)

## Error

```
--- FAIL: TestELSyncSafeRetractedByOffset (72.06s)
assertions.go:387:
Error Trace: /home/circleci/project/op-devstack/dsl/check.go:26
/home/circleci/project/op-devstack/presets/singlechain_from_runtime.go:51
/home/circleci/project/op-devstack/presets/singlechain_multinode.go:22
/home/circleci/project/op-acceptance-tests/tests/sync/elsync/offset_el_safe/init_test.go:15
/home/circleci/project/op-acceptance-tests/tests/sync/elsync/offset_el_safe/sync_test.go:28
Error: Received unexpected error:
operation failed permanently after 30 attempts: expected head to match: safe
```

## Context

The failure is during **preset setup**, before the test body runs — `singlechain_from_runtime.go:51` is the preset's initial CrossSafe/LocalUnsafe sync check, identical symptom to #19897. The preset waits up to 30×2s = 60s for the verifier CL to reach `types.CrossSafe` matching the sequencer.

The preset in `init_test.go` configures `VerifierSyncMode = nodeSync.ELSync` + `OffsetELSafe = 10s` for both L2CLs globally. In ELSync mode, `CrossSafe` requires derivation + supervisor confirmation of old batched data — slower than blocks arriving via EL p2p.

## Related

- #19897 — `TestTruncateDatabaseOnELResync`: same preset hook, same error message, also ELSync mode. Likely same root cause (CrossSafe promotion slower than 60s budget when under CI resource contention).

## Date

2026-04-24

Start with op-acceptance-tests/tests/sync/elsync/offset_el_safe/init_test.go and sync_test.go, then trace the preset setup through op-devstack/presets/singlechain_from_runtime.go:51 and singlechain_multinode.go:22. Compare the failure with #19897 and reproduce the CrossSafe timeout under CI-like contention. Done means the preset setup completes reliably and TestELSyncSafeRetractedByOffset passes.

Written by the indexing model from the issue text.