feat(driver): upgrade node for Unzen fork

[YoGhurt111]

Summary

• add alethia-reth:v1.3.0 as the default Mainnet execution engine while keeping taiko-geth:v2.6.0 as a fallback
• upgrade the Mainnet driver to taiko-alethia-client-v2.6.0
• align driver flags with the Unzen configuration by using --inbox, removing legacy fork/whitelist flags, and sharing the execution engine JWT with preconfirmations
• preserve the legacy l2_execution_engine profile as a Geth compatibility alias for existing node configurations
• add optional Reth snapshot data-directory and discovery-port configuration

Why

Mainnet needs the same execution-engine and driver configuration updates already exercised on Hoodi, together with the contract and flag changes from taikoxyz/k8s-configs#1338.

Operator impact

New configurations default to reth_execution_engine. Existing .env files using COMPOSE_PROFILES=l2_execution_engine continue to start the Geth-based stack without requiring an immediate environment migration.

Validation

• git diff --check
• sh -n script/start-driver.sh
• rendered Docker Compose configurations for reth_execution_engine, geth_execution_engine, and the legacy l2_execution_engine profile
• simulated driver arguments for Reth, Geth, and legacy profiles
• verified amd64 and arm64 image manifests for alethia-reth v1.3.0, taiko-geth v2.6.0, and taiko-client v2.6.0

Reference

• taikoxyz/k8s-configs#1338