Implement transaction execution pipeline

[mw2000]

Summary

Build the end-to-end transaction execution pipeline that takes a wire-format transaction and produces a state transition. Currently eevm can execute raw bytecode but has no pipeline for: decode tx → validate → deduct gas → execute → apply state changes → generate receipt.

Specification

The pipeline:

1. Decode — deserialize from wire format using Transaction.Envelope.decode/1
2. Recover sender — via Transaction.Signer.recover_sender/2
3. Validate — via Transaction.Validator.validate/3
4. Deduct upfront cost — gas_limit * gas_price + value from sender balance
5. Calculate intrinsic gas — via Transaction.IntrinsicGas.calculate/1
6. Set up execution context — populate Context.Transaction, Context.Block, Context.Contract
7. Pre-warm access set — sender, recipient, coinbase, precompiles, access list entries
8. Execute EVM — EEVM.execute/2 for message calls, or CREATE for contract deployment
9. Apply gas refund — min(refund, gas_used / 5) back to sender
10. Transfer priority fee — to coinbase
11. Generate receipt — status, cumulative gas, logs, bloom

Implementation Guide

1. Create lib/eevm/transaction/executor.ex — the pipeline orchestrator
2. Define EEVM.TransactionResult struct — status, gas_used, logs, receipt, state changes
3. Wire together existing modules: Envelope, Signer, Validator, IntrinsicGas, Database, EEVM.execute
4. Handle all tx types — Legacy, AccessList, FeeMarket, Blob (and eventually SetCode)
5. Tests: execute a simple value transfer, execute a contract call, contract deployment, failed tx (validation error), reverted tx

Acceptance Criteria

• Full pipeline from wire bytes to state transition
• Sender balance deducted upfront, refund applied after
• Priority fee transferred to coinbase
• Works for all 4 tx types
• Contract deployment via tx (to=nil)
• Failed validation returns error without state change
• Reverted tx still charges gas
• Tests pass

Reference

• Ethereum Yellow Paper §6 (Transaction Execution)
• execution-specs: ethereum/execution-specs state_transition function