### Task 2: Build the valueless six-decimal mock asset with TDD

**Files:**
- Create: `src/MockUSDC.sol`
- Create: `test/MockUSDC.t.sol`

**Interfaces:**
- Produces `MockUSDC.mint(address,uint256)`, `decimals() == 6`, and standard ERC-20 behavior.
- Consumed by the bank tests, deployment scripts, and dashboard ABI export.

- [ ] Write `test/MockUSDC.t.sol` first. Cover the exact name/symbol/decimals, owner-only mint, successful mint, transfer/approve behavior inherited from ERC-20, and zero initial supply. Use `vm.expectRevert(abi.encodeWithSelector(Ownable.OwnableUnauthorizedAccount.selector, stranger))` for non-owner minting.

- [ ] Run the focused test and observe red:

```bash
forge test --match-path test/MockUSDC.t.sol -vvv --force
```

Expected red: `src/MockUSDC.sol` is missing.

- [ ] Implement only the tested contract:

```solidity
/// @notice Educational mock token with no monetary value. Never use as real USDC.
contract MockUSDC is ERC20, Ownable {
    constructor(address initialOwner) ERC20("Mock USD Coin", "mUSDC") Ownable(initialOwner) {}

    function decimals() public pure override returns (uint8) { return 6; }
    function mint(address to, uint256 amount) external onlyOwner { _mint(to, amount); }
}
```

Reject a zero `initialOwner` through OpenZeppelin’s `OwnableInvalidOwner` behavior. Do not add faucet, burn, permit, blacklist, proxy, or bank-specific logic.

- [ ] Run red-to-green verification:

```bash
forge fmt
forge test --match-path test/MockUSDC.t.sol -vvv --force
```

Expected: all mock-token tests pass.

- [ ] Commit:

```bash
git add src/MockUSDC.sol test/MockUSDC.t.sol
git commit -m "feat: add valueless mock USDC"
```

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