Summary

Clarify that when a state gas charge exceeds state_gas_reservoir and spills into gas_left, the charge still increments execution_state_gas_used in full — it does not increment execution_regular_gas_used. Counter classification is by cost type, not funding source.

Motivation

Discovered during bal-devnet-3 debugging. Three EL clients diverged on the same block because they disagreed on which counter a spilled state-gas charge increments:

• geth: increments execution_state_gas_used (matches EELS charge_state_gas in forks/amsterdam/vm/gas.py).
• erigon / reth / nethermind: incremented execution_regular_gas_used (read line 117 as "costs that were paid from the regular budget count toward regular gas").

Since block_gas_used = max(cum_regular_gas_used, cum_state_gas_used), the two interpretations produce block totals that differ by exactly the spilled amount (e.g. 131,488 = 112 × cpsb for a single GAS_NEW_ACCOUNT at 100M gas limit), splitting the chain.

The current paragraph at line 117 already implies the EELS / geth behaviour but does not state it explicitly. Adding one sentence at line 111, where spillover is introduced, removes the ambiguity at the point readers are most likely to lose the invariant.

Scope

Purely a clarification — no semantic change. Disjoint from:

• Update EIP-8037: clarify state gas behavior on frame failure (child vs top-level) #11468 / Update EIP-8037: Refund state gas on all frame failures including top level #11476 — restoration behaviour on frame failure (touch line 114, leave line 111 untouched).
• Update EIP-8037: add additional tx validity condition #11503 — tx inclusion validity condition.
• merged Update EIP-8037: clarify reservoir mechanics #11328 / Update EIP-8037: clarify regular gas must be charged before state gas #11421 / Update EIP-8037: Align with EIP-7928 Gas Validation Phases #11414 — reservoir mechanics, regular-first ordering, EIP-7928 phase alignment (none introduced the spillover-classification rule).

EELS already implements this behaviour in charge_state_gas (src/ethereum/forks/amsterdam/vm/gas.py):

if evm.state_gas_left >= amount:
    evm.state_gas_left -= amount
elif evm.state_gas_left + evm.gas_left >= amount:
    remainder = amount - evm.state_gas_left
    evm.state_gas_left = Uint(0)
    evm.gas_left -= remainder
else:
    raise OutOfGasError

evm.state_gas_used += amount  # full amount, regardless of source

This PR brings the EIP text in line with the reference implementation.