fix overflow expression for number of pages in sequence interface

[lucaslie]

see title

[Copilot]

Pull Request Overview

This PR fixes an overflow calculation issue in the attention interface's sequence page allocation logic. The change corrects how the number of pages is computed when sequences require additional pages beyond the basic allocation.

• Modified the overflow check calculation to use per-sequence token allocation instead of total tokens
• Updated the comment to better explain the overflow detection logic

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