state-actor ethrex: OOM fixed upstream, image repoint pending

[CPerezz]

Status update on the 350 GB ethrex failure (this repo's runs 29930270176 / 29945931818):

• fix(ethrex): bound peak RSS so large --target-size runs stop OOM-killing (closes #116) ethereum/state-actor#117 merged: OOM fixed, writer now ~2× faster than the other clients (150 GB in 47 min, peak RSS ~4.4 GiB, genesis roots unchanged).
• state-actor: point ethrex image back to :main #30 repoints state-actor-ethrex:pr-117 → :main.
• Remaining blocker for 350 GB is disk, not memory: ethrex realizes ≈1.8× target (~700 GB + ~0.5× transient spill) — sizecal: ethrex disk cost is ~2x bytesPerSlot (trie + flat rows per slot); docs/CALIBRATION.md missing ethereum/state-actor#128 tracks the accounting.