…class has an empty constructor (#21562)

## Summary

When a TypeScript class used a computed-key static property together with a constructor that has no parameter-property assignments, the early return in `transform_class_fields` dropped the `computed_key_assignment_static_block` that initializes the temp var, leaving it declared but never assigned.

```ts
export class SampleClass {
  static [Symbol.toPrimitive] = "test"
  constructor() {}
}
```

previously emitted:

```js
let _Symbol$toPrimitive;
export class SampleClass {
  static {
    this[_Symbol$toPrimitive] = "test";
  }
  constructor() {}
}
```

Now emits (matching TypeScript's own output under `useDefineForClassFields: false`):

```js
let _Symbol$toPrimitive;
export class SampleClass {
  static {
    _Symbol$toPrimitive = Symbol.toPrimitive;
  }
  static {
    this[_Symbol$toPrimitive] = "test";
  }
  constructor() {}
}
```

## Test plan

- Added fixtures `computed-static-property-with-constructor` (exact repro) and `computed-static-property-with-constructor-super` (super() + multiple computed keys) under `babel-plugin-transform-typescript`.
- Verified output against `tsc` 5.7 with `useDefineForClassFields: false`.

Closes rolldown/rolldown#9121

…class has an empty constructor (#21562)

## Summary

When a TypeScript class used a computed-key static property together with a constructor that has no parameter-property assignments, the early return in `transform_class_fields` dropped the `computed_key_assignment_static_block` that initializes the temp var, leaving it declared but never assigned.

```ts
export class SampleClass {
  static [Symbol.toPrimitive] = "test"
  constructor() {}
}
```

previously emitted:

```js
let _Symbol$toPrimitive;
export class SampleClass {
  static {
    this[_Symbol$toPrimitive] = "test";
  }
  constructor() {}
}
```

Now emits (matching TypeScript's own output under `useDefineForClassFields: false`):

```js
let _Symbol$toPrimitive;
export class SampleClass {
  static {
    _Symbol$toPrimitive = Symbol.toPrimitive;
  }
  static {
    this[_Symbol$toPrimitive] = "test";
  }
  constructor() {}
}
```

## Test plan

- Added fixtures `computed-static-property-with-constructor` (exact repro) and `computed-static-property-with-constructor-super` (super() + multiple computed keys) under `babel-plugin-transform-typescript`.
- Verified output against `tsc` 5.7 with `useDefineForClassFields: false`.

Closes rolldown/rolldown#9121

…class has an empty constructor (#21562)

## Summary

When a TypeScript class used a computed-key static property together with a constructor that has no parameter-property assignments, the early return in `transform_class_fields` dropped the `computed_key_assignment_static_block` that initializes the temp var, leaving it declared but never assigned.

```ts
export class SampleClass {
  static [Symbol.toPrimitive] = "test"
  constructor() {}
}
```

previously emitted:

```js
let _Symbol$toPrimitive;
export class SampleClass {
  static {
    this[_Symbol$toPrimitive] = "test";
  }
  constructor() {}
}
```

Now emits (matching TypeScript's own output under `useDefineForClassFields: false`):

```js
let _Symbol$toPrimitive;
export class SampleClass {
  static {
    _Symbol$toPrimitive = Symbol.toPrimitive;
  }
  static {
    this[_Symbol$toPrimitive] = "test";
  }
  constructor() {}
}
```

## Test plan

- Added fixtures `computed-static-property-with-constructor` (exact repro) and `computed-static-property-with-constructor-super` (super() + multiple computed keys) under `babel-plugin-transform-typescript`.
- Verified output against `tsc` 5.7 with `useDefineForClassFields: false`.

Closes rolldown/rolldown#9121

### 🐛 Bug Fixes

- 48967e8 isolated_declarations: Drop required type check for private
parameter properties on private constructors (#21515) (Dunqing)
- 91e5bde transformer/typescript: Preserve computed-key static block
when class has an empty constructor (#21562) (Dunqing)
- 50e9d26 mangler: Assign correct slot to shadowed function-expression
names (#21535) (Dunqing)
- 065ce47 isolated_declarations: Collect types from private accessors
for paired inference (#21516) (Dunqing)
- 00fc136 codegen: Preserve coverage comments before object properties
(#21312) (bab)
- d676e0c minifier: Mark LHS of `??=` as read when converting from `==
null &&` (#21546) (Gunnlaugur Thor Briem)

### ⚡ Performance

- e45efc5 parser: Reduce `try_parse` usage in favour of `lookahead`
(#21532) (Boshen)
- ddb1bf8 parser: Avoid redundant `IdentifierReference` clone in
shorthand property (#21511) (Boshen)
- be2b392 allocator: Store pointers directly in `Arena` (#21483)
(overlookmotel)

Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>
Co-authored-by: Cameron <cameron.clark@hey.com>