ICE in `TypeChecker::visit(UnaryOperation)` when duplicate `using for` unary operator bindings include a self-referential call

The compiler panics with `Solidity assertion failed` in [`libsolidity/analysis/TypeChecker.cpp:1641`](https://github.com/ethereum/solidity/blob/9be66192f9db40e5a43f71fc78e06b2f35e9ccdd/libsolidity/analysis/TypeChecker.cpp#L1641) when two functions are bound to the same unary operator via `using for` and one of them uses that operator in its own body.

The root cause is similar to #16616, but the crash site is different. Maybe they should be fixed in one PR.

MRE:
```solidity
type T is int256;
function neg1(T a) pure returns (T) { return -a; }
function neg2(T a) pure returns (T) { return a; }
using {neg1 as -, neg2 as -} for T global;
```

Reproduce: save as `mre.sol`, run `solc --bin mre.sol`.

Output:
```
Internal compiler error:
/solidity/libsolidity/analysis/TypeChecker.cpp(1641): Throw in function virtual bool solidity::frontend::TypeChecker::visit(const solidity::frontend::UnaryOperation&)
Dynamic exception type: boost::wrapexcept
std::exception::what: Solidity assertion failed
[solidity::util::tag_comment*] = Solidity assertion failed
```

Expected behavior: a type error about duplicate unary operator bindings for `-` before any operator expression is type-checked.

Git commit: 9be66192f
solc 0.8.35-develop.2026.4.18+commit.9be66192.Linux.g++

Start with libsolidity/analysis/TypeChecker.cpp at line 1641 and reproduce the ICE using the provided mre.sol and `solc --bin mre.sol` command. Trace how duplicate `using for` unary bindings are handled before the self-referential operator expression is type-checked; done means the compiler reports a duplicate unary operator binding type error instead of panicking.

Written by the indexing model from the issue text.