fix(evm): restore frame gas after inspector callback to preserve rescue_gas

[krabat-l]

Summary

When an inspector is attached (e.g. TracerEip3155), frame_end is called after each subcall frame completes, which triggers GasInspector::call_end → gas.spend_all() for any error result (including OutOfGas).
This happens in both inspect_frame_run and inspect_frame_init, before frame_return_result has a chance to call rescue_gas().

MegaETH's rescue_gas mechanism saves gas.remaining() from frames halted by additional limits (state growth, compute gas, etc.) to refund the sender in last_frame_result.
With the inspector path, spend_all() zeroes gas.remaining() first, so rescue_gas() always reads 0 — the refund is lost.
This causes different gas_used values compared to the non-inspector path, producing a receipts root mismatch when validating blocks with an inspector attached.

Fix: in both inspect_frame_init and inspect_frame_run, save gas.remaining() before calling frame_end, then restore it if the inspector callback reduced it.

Root cause trace

inspect_frame_run / inspect_frame_init
  └─ frame_end(ctx, inspector, ..., frame_result)
       └─ TracerEip3155::call_end
            └─ GasInspector::call_end
                 └─ if is_error() { gas.spend_all() }   ← zeroes remaining gas

(later, in the exec loop)
frame_return_result(result)
  └─ before_frame_return_result
       └─ if check_limit().exceeded_limit() { rescue_gas(result.gas()) }
            └─ self.rescued_gas += gas.remaining()      ← reads 0, should be > 0

Verification

Validated against block 3021764 on MegaETH mainnet:

• Without inspector: block validates correctly
• With TracerEip3155 before fix: receipts root mismatch
• With TracerEip3155 after fix: block validates correctly