Storage layout y upgrades

# Ethereum storage layout lab

Version: `2.0.44-alpha.1`

Copy `templates/` into `.tmp/storage-layout-lab`, then run (from the repository root):

```bash
node tools/labs/ethereum-storage-layout-lab/preflight.mjs
mkdir -p .tmp/storage-layout-lab
cp -R tools/labs/ethereum-storage-layout-lab/templates/. .tmp/storage-layout-lab/
cd .tmp/storage-layout-lab
forge inspect StorageLab storageLayout
forge inspect StorageLabUnsafeV2 storageLayout
forge test -vv
```

Compare the slot, offset, byte width and type of every field. The unsafe V2 intentionally changes the first slots; it is evidence, not a deployment recommendation.

The test reads raw slots with `sload` and checks the exact packed words: slot 0 = `owner | counter << 160`, slot 1 = `enabled | mode << 8`, and `credits[deployer]` at `keccak256(abi.encode(deployer, 2))`.

Cleanup removes `.tmp/storage-layout-lab` (`rm -rf .tmp/storage-layout-lab`). No Anvil process is needed for this lab.

import { spawnSync } from 'node:child_process';
import { existsSync } from 'node:fs';

const commands = ['forge', 'anvil', 'cast'];
const versions = Object.fromEntries(
  commands.map((command) => {
    const result = spawnSync(command, ['--version'], { encoding: 'utf8' });
    return [command, { available: result.status === 0, version: (result.stdout || result.stderr || result.error?.message || '').trim().split('\n')[0] }];
  })
);
const artifacts = [
  'tools/labs/ethereum-storage-layout-lab/templates/foundry.toml',
  'tools/labs/ethereum-storage-layout-lab/templates/src/StorageLab.sol',
  'tools/labs/ethereum-storage-layout-lab/templates/test/StorageLab.t.sol',
];
const missing = artifacts.filter((artifact) => !existsSync(artifact));

console.log(JSON.stringify({ versions, missing }, null, 2));
if (commands.some((command) => !versions[command].available) || missing.length) process.exit(1);

[profile.default]
src = "src"
test = "test"
out = "out"
solc_version = "0.8.28"
optimizer = true
optimizer_runs = 200

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.28;

contract StorageLab {
    address public owner;
    uint96 public counter;
    bool public enabled;
    uint16 public mode;
    mapping(address => uint256) public credits;

    constructor() {
        owner = msg.sender;
        counter = 7;
        enabled = true;
        mode = 42;
        credits[msg.sender] = 100;
    }

    function rawSlot(uint256 slot) external view returns (bytes32 value) {
        assembly {
            value := sload(slot)
        }
    }
}

// Deliberately incompatible with StorageLab: do not use as an upgrade.
contract StorageLabUnsafeV2 {
    uint256 public counter;
    address public owner;
    bool public enabled;
    uint16 public mode;
    mapping(address => uint256) public credits;
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.28;

import {StorageLab} from "../src/StorageLab.sol";

contract StorageLabTest {
    function testInitialStateAndPacking() public {
        StorageLab lab = new StorageLab();
        require(lab.owner() == address(this), "owner");
        require(lab.counter() == 7, "counter");
        require(lab.enabled(), "enabled");
        require(lab.mode() == 42, "mode");
        require(lab.credits(address(this)) == 100, "credits");

        // Slot 0: owner (bytes 0..19) + counter (bytes 20..31).
        bytes32 expectedSlot0 = bytes32((uint256(7) << 160) | uint256(uint160(address(this))));
        require(lab.rawSlot(0) == expectedSlot0, "slot 0 packs owner + counter");

        // Slot 1: enabled (byte 0) + mode (bytes 1..2).
        bytes32 expectedSlot1 = bytes32((uint256(42) << 8) | uint256(1));
        require(lab.rawSlot(1) == expectedSlot1, "slot 1 packs enabled + mode");

        // Slot 2 is the mapping marker; the value lives at keccak256(key . slot).
        require(lab.rawSlot(2) == bytes32(0), "mapping marker slot stays empty");
        uint256 creditSlot = uint256(keccak256(abi.encode(address(this), uint256(2))));
        require(uint256(lab.rawSlot(creditSlot)) == 100, "credits[deployer] at keccak slot");
    }
}

cd ../..
rm -rf .tmp/storage-layout-lab