fix(e2e): set anvilSlotsInAnEpoch in offchain payment test to prevent premature finalization

[AztecBot]

Summary

The e2e_offchain_payment test's reorg test case fails with "Cannot rollback to block 8 as it is before finalized 9" because PR #21156 (Properly compute finalized block) changed Anvil's default --slots-in-an-epoch to 1, causing blocks to be finalized almost immediately (finalized = latest - 2).

The fix sets anvilSlotsInAnEpoch: 32 in the test's setup, matching the same pattern used by epochs_l1_reorgs.parallel.test.ts which was updated in #21156.

Details

• Root cause: Two changes collided on merge-train/fairies — the offchain reception feature (feat: offchain reception #20893) added a test with forceReorg(), while chore: Properly compute finalized block #21156 changed L1 finality behavior. The test's rollback target was already finalized by the time it executed.
• Fix: Delay Anvil finalization by using 32 slots/epoch (matching real Ethereum mainnet), so blocks stay unfinalized long enough for the reorg test.
• Full analysis: https://gist.github.com/AztecBot/95548058701d1aaf0a8635d2f2d30886"

ClaudeBox log: https://claudebox.work/s/2cc546f52c926894?run=1

[ludamad]

Closing as duplicate — superseded by a newer attempt.