fix: layout and pagination items overlap

[devnatan]

Fixes layout and pagination items overlap. The use case is: when you need to render the "empty slots" of pagination with a placeholder item. Currently this is not possible but it is not the indeed behavior.

Create a pagination using some character as layout target then use layoutSlot(<the same character>).

✅ Expected behavior:

1. Pagination renders first
2. layoutSlot([...]) renders in the slots that pagination couldn't reach (due to not enough source)
3. Changing pages only affects Pagination

❌ Current behavior:

1. layoutSlot([...]) renders in all slots
2. Pagination renders "below" (IF supports Overlapping Items so there's a "above"/"below" concept) layoutSlot
3. Changing pages only affects Pagination

Sample code:

State<Pagination> paginationState = buildLazyPaginationState([...])
    .layoutTarget('#')
    .build()

// onFirstRender
render.layoutSlot('#', [...placeholderItem]);

This PR also removes layoutSlot('O') restriction.

Before	After
Gravando.2025-08-02.141152.mp4	Gravando.2025-08-02.140331.mp4