let/const in try...catch are not block-scoped

```javascript
for ( let i = 0; i < 10; i += 1 ) {
try {
const square = i * i;
setTimeout( () => console.log( square ), i * 100 );
} catch (e) {}
}
```
Generates:
```javascript
for ( var i = 0; i < 10; i += 1 ) {
try {
var square = i * i;
setTimeout( function () { return console.log( square ); }, i * 100 );
} catch (e) {}
}
```

Start with the JavaScript example and compare it with the generated output, focusing on let/const handling inside try...catch and the loop. Reproduce the transformation, then verify that the generated code preserves block scoping and the per-iteration value used by the delayed callback.

Written by the indexing model from the issue text.