ci: Add Foundry tooling integration test (#511)

## Description

Adds a CI workflow that builds and tests a small Foundry project with
`foundry-polkadot`'s `forge`, exercising the standard JSON interface
between `resolc` and `foundry-polkadot` end-to-end.

## Resolved Issues

Closes #513

tooling-projects/foundry/erc20/foundry.toml

@@ -0,0 +1,25 @@
+[profile.default]
+src = "src"
+test = "test"
+libs = ["lib"]
+solc = "0.8.35"
+remappings = [
+    "forge-std/=lib/forge-std/src/",
+    "@openzeppelin/contracts/=lib/openzeppelin-contracts/contracts/",
+]
+extra_output = [
+    "abi",
+    "metadata",
+    "devdoc",
+    "userdoc",
+    "storageLayout",
+    "ir",
+    "irOptimized",
+    "evm.bytecode",
+    "evm.deployedBytecode",
+    "evm.assembly",
+    "evm.methodIdentifiers",
+]
+
+[profile.default.polkadot]
+resolc_compile = true

tooling-projects/foundry/erc20/src/MyToken.sol

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: MIT
+// Compatible with OpenZeppelin Contracts ^5.0.0
+pragma solidity ^0.8.22;
+
+import { ERC20 }   from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
+
+contract MyToken is ERC20, Ownable {
+    constructor(address initialOwner)
+        ERC20("MyToken", "MTK")
+        Ownable(initialOwner)
+    {}
+
+    function mint(address to, uint256 amount) public onlyOwner {
+        _mint(to, amount);
+    }
+}

tooling-projects/foundry/erc20/test/MyToken.t.sol

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.22;
+
+import { Test } from "forge-std/Test.sol";
+import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
+import { MyToken } from "../src/MyToken.sol";
+
+contract MyTokenTest is Test {
+    MyToken internal token;
+    address internal owner = address(this);
+    address internal alice = address(0xA11CE);
+    address internal bob   = address(0xB0B);
+
+    function setUp() public {
+        token = new MyToken(owner);
+    }
+
+    function test_NameAndSymbol() public view {
+        assertEq(token.name(), "MyToken");
+        assertEq(token.symbol(), "MTK");
+    }
+
+    function test_Owner() public view {
+        assertEq(token.owner(), owner);
+    }
+
+    function test_OwnerCanMint() public {
+        token.mint(alice, 1000);
+        assertEq(token.balanceOf(alice), 1000);
+    }
+
+    function test_NonOwnerCannotMint() public {
+        vm.prank(alice);
+        vm.expectRevert(
+            abi.encodeWithSelector(Ownable.OwnableUnauthorizedAccount.selector, alice)
+        );
+        token.mint(alice, 1000);
+    }
+
+    function test_TotalSupplyIncreases() public {
+        uint256 before = token.totalSupply();
+        token.mint(alice, 500);
+        assertEq(token.totalSupply() - before, 500);
+    }
+
+    function test_Transfer() public {
+        token.mint(owner, 1000);
+        assertTrue(token.transfer(alice, 100));
+        assertEq(token.balanceOf(alice), 100);
+        assertEq(token.balanceOf(owner), 900);
+    }
+
+    function test_TransferFrom() public {
+        token.mint(owner, 1000);
+        token.approve(alice, 50);
+        vm.prank(alice);
+        assertTrue(token.transferFrom(owner, bob, 50));
+        assertEq(token.balanceOf(bob), 50);
+        assertEq(token.allowance(owner, alice), 0);
+    }
+}

tooling-projects/foundry/erc20/verify-compiler-output.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+
+# Asserts that the compiled project contains the expected compiler output.
+# Requires `forge` in PATH. Run from the project's root.
+#
+# Usage: verify-compiler-output.sh <resolc-path>
+
+set -euxo pipefail
+
+if [[ $# -ne 1 ]]; then
+    echo "usage: $(basename "$0") <resolc-path>" >&2
+    exit 2
+fi
+
+resolc=$1
+
+inspect() {
+    forge inspect --use-resolc "$resolc" MyToken "$@"
+}
+
+inspect bytecode          | grep '^0x50564d'                      > /dev/null
+inspect deployedBytecode  | grep '^0x50564d'                      > /dev/null
+inspect irOptimized       | grep .                                > /dev/null
+inspect ir                | grep .                                > /dev/null
+inspect assembly          | grep .                                > /dev/null
+inspect abi               --json | jq -e 'length > 0'             > /dev/null
+inspect methodIdentifiers --json | jq -e 'length > 0'             > /dev/null
+inspect storageLayout     --json | jq -e '.storage | length > 0'  > /dev/null
+inspect metadata          --json | jq -e 'length > 0'             > /dev/null
+inspect devdoc            --json | jq -e 'length > 0'             > /dev/null
+inspect userdoc           --json | jq -e 'length > 0'             > /dev/null
+
+echo "all checks passed"