dev-20260224-base-token-holder

feat: remove l2 base token hook + add update saved total supply

Remove the l2_base_token system hook (withdraw/withdrawWithMessage) as
base token withdrawals are now handled by Solidity system contracts.
Add update_saved_total_supply to mint_token path to replicate
L2AssetTracker's _getOrSaveTotalSupply logic natively.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>