False positive: java/field-masks-super-field triggered on Kotlin sealed class with open val constructor parameters

## Summary
The rule `java/field-masks-super-field` is producing a false positive on a Kotlin `sealed class` that uses `open val` constructor parameters. No actual field shadowing exists in the source code.

## CodeQL Version
GitHub Advanced Security (cloud) - latest on github.dev

## Language
Kotlin (analysed via Java extractor)

## Minimal Reproduction

```kotlin
sealed class ImageType(open val width: Int, open val height: Int) {
object Portrait : ImageType(78, 98)
object Square : ImageType(78, 78)
object PortraitLarge : ImageType(163, 205)
}
```

## What CodeQL Reports
> "This field shadows another field called `width`/`height` in a superclass."

Rule ID: `java/field-masks-super-field`

## Why This Is a False Positive
- No subclass redeclares `width` or `height` in its body
- Every `object` subclass simply passes values via the constructor to the parent
- There is no Java-style field shadowing at the source level
- The alert appears to be triggered by synthetic bridge method scaffolding
that Kotlin generates for `open val` properties, which the Java extractor
misidentifies as a field declaration in the subclass

## Related
This appears to be in the same category as PR #10859 which excluded Kotlin Live Literals from this same rule:
https://github.com/github/codeql/pull/10859

That PR acknowledged that Kotlin-generated bytecode patterns can trigger false positives in `java/field-masks-super-field`. The `sealed class` + `object` + `open val` pattern appears to be another such case.

## Workaround
Removing `open` from the constructor parameters eliminates the alert and is safe when no subclass actually overrides the properties. However
this forces unnecessary code changes to work around a false positive.

## Expected Behaviour
The rule should not fire when no subclass explicitly redeclares the field in its body - consistent with how PR #10859 handled Live Literals.

Start with the Kotlin reproduction and the java/field-masks-super-field query, then compare its handling with PR #10859 on Kotlin Live Literals. Confirm how the sealed class, object subclasses, and open val parameters are represented by the Java extractor. Done means the alert is suppressed for this pattern while genuine field shadowing remains reported.

Scritto dal modello di indicizzazione a partire dal testo della issue.