fix edge case for repetition count threshold

[SergeySklyarov]

Overview

Fixes an edge case where a repetition count of exactly 2000 was rejected by the parser, despite values above 2000 being handled as unbounded. Repetition counts equal to the threshold of 2000 are now accepted, while nested repetitions exceeding the expansion limit remain restricted.

Additional information

This PR revisits the fix from #27177 (which stalled in Draft due to template and AI disclosure requirements) and presents the solution along with tests.

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: YES — Codex assisted with implementation and test preparation; I reviewed the change and ran the parser test locally.

[ggml-gh-bot]

Hi @SergeySklyarov, thanks for your contribution!

Per our contribution guidelines, the automated PR checker found the following issue(s) that need your attention:

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[SergeySklyarov]

Hi @ggerganov could you please check this PR when you have time?

[SergeySklyarov]

Hi @ggerganov, following up on this PR. It has no merge conflicts and #28279 has already been merged. Could you please review it and approve the pending CI workflows when convenient?

[ggerganov]

Hm, we made this change recently in #28469. cc @aldehir