Fix explicit named slots ommited during component folding

[ghabriel25]

Summary

Follow-up to #209: whitespace-only explicit named slots are registered as empty slots during folding instead of being dropped.

Problem

#209 correctly avoided creating non-empty placeholders for whitespace-only content (placeholders made $slot->isEmpty() false during fold-time pre-render).

For explicit named slots it used continue, so the slot was omitted from $__slots during pre-render:

<x-card>
    <x-slot:footer> </x-slot>
</x-card>

Path	$footer during fold pre-render
Blade / SlotCompiler (runtime)	Defined, ComponentSlot('') after trim()
Fold after #209	Undefined (missing from $__slots)

Fold treats slots as pass-through (placeholder → restore). Omitting the slot can break pre-render of templates that echo the named slot ({{ $footer }}) when the only content is whitespace.

Default $slot is unaffected: Wrapper already does $__slots['slot'] ??= new ComponentSlot('').

Changes

In Foldable::setupSlots(), always register explicit slots:

• Has real content → placeholder TextNode + slotByPlaceholder (unchanged)
• Whitespace-only / empty → empty children ([]), no placeholder

$children = [];

if ($this->hasActualContent($child->children)) {
    $placeholder = 'BLAZE_PLACEHOLDER_' . $this->placeholderIndex++ . '_';
    $this->slotByPlaceholder[$placeholder] = $child;
    $children = [new TextNode($placeholder)];
}

$slots[$child->name] = new SlotNode(
    // ...
    children: $children,
    // ...
);

Implicit default-slot behavior from #209 is unchanged: whitespace-only loose content does not synthesize a default slot.

[ghabriel25]

@ganyicz Could you review this? I think I made a regression from previous PR, thanks!

[github-actions]

Benchmark Result: Default

Attempt	Blade	Blaze	Change
#1	367.07ms	14.85ms	96%
#2	367.89ms	14.91ms	95.9%
#3	359.84ms	14.92ms	95.9%
#4	361.36ms	14.96ms	95.9%
#5	356.38ms	14.74ms	95.9%
#6	360.46ms	15.09ms	95.8%
#7	364.54ms	14.95ms	95.9%
#8	363.75ms	15.01ms	95.9%
#9 *	369.80ms	15.22ms	95.9%
#10	363.19ms	15.03ms	95.9%
Snapshot	364.54ms	14.79ms	95.9%
Result	363.19ms (~)	14.95ms (~)	95.9% (~)

_{Median of 10 attempts (* = outlier, excluded from result), 5000 iterations x 10 rounds, 47.74s total}

_{To run a specific benchmark, comment /benchmark <name>
attributes, aware, class, default, forwarding, merge, named-slots, no-attributes, slot, compilation}

[ganyicz]

Oof good catch, thanks @ghabriel25