`packages/codegen` drops required parentheses around the right operand of a private-in expression when that operand is another relational expression. This changes which value the private-field check receives and can change observable behavior.
For example, this input throws a `TypeError`:
```js
class C {
#x;
test(a, b) {
return #x in (a instanceof b);
}
}
new C().test({}, Object);
```
`a instanceof b` evaluates to `true`, but a private-field check requires an object on its right-hand side.
The JavaScript printer previously emitted:
```js
return #x in a instanceof b;
```
Relational operators associate to the left, so that output is parsed as `(#x in a) instanceof b`. The private-field check on `{}` produces `false`, and `false instanceof Object` returns `false` instead of throwing.
The printer now preserves the original grouping:
```js
return #x in (a instanceof b);
```
`printPrivateInExpression` now prints its right operand with `PREC_COMPARE` instead of `PREC_EQUALS`. The expression printers wrap operands whose precedence is equal to or lower than the requested precedence, so the comparison threshold retains parentheses around `<`, `<=`, `>`, `>=`, `instanceof`, and nested private-in expressions. The now-unused `PREC_EQUALS` import is removed.
Equality and lower-precedence operands continue to retain their required grouping. Shift, arithmetic, and exponentiation operands can still omit unnecessary parentheses. The existing `CTX_FORBID_IN` handling remains in place.
This applies to both ordinary and source-map-enabled printer builds and brings the JavaScript implementation in line with the Rust fix in #26411. It addresses grouping of the private-in right operand, separately from the left-operand correction in #26403.
camc314