[TomasVotruba]

Closes #352.

ForbiddenStaticClassConstFetchRule flagged every static::SOME_CONST fetch. But late static binding is meaningful when a child class overrides the constant - the value genuinely changes per class, which is the intended use.

Rule now uses PHPStan collectors:

• StaticClassConstFetchCollector - records each static::CONST fetch (skips static::class magic and abstract classes)
• ClassConstantDeclarationCollector - records each class, its parent and the constants it declares

The rule reports a fetch only when no child class overrides that constant; when a child redeclares it, the fetch is kept. static::class is always allowed.

How it works

Reported - no child overrides the constant, so static:: behaves like self:::

class SomeClass
{
    protected const SOME_CONST = 'value';

    public function run()
    {
        return static::SOME_CONST; // error
    }
}

Skipped - a child class overrides the constant, so late static binding changes the value on purpose:

class ParentClass
{
    protected const SOME_CONST = 'parent';

    public function run()
    {
        return static::SOME_CONST; // no error
    }
}

class ChildClass extends ParentClass
{
    protected const SOME_CONST = 'child';
}

Skipped - static::class is late static binding magic, not an overridable constant:

class SomeClass
{
    public function run()
    {
        return static::class; // no error
    }
}

Builds on the failing fixture from #373.

Fixtures cover: child overrides const (skip), child without override (report), static::class (skip).