BufferedTokenizer silently drops data when oversize input has no delimiters

[yaauie]

Logstash information:

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1. Logstash version (e.g. bin/logstash --version): 9.2.0-SNAPSHOT
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Description of the problem including expected versus actual behavior:

In #17229 changes to the buffered tokenizer introduce an edge-case where an oversized sequence of bytes that do not include a delimiter can be silently dropped.

This occurs because size validation happens after the token is fully accumulated, which does not occur if no trailing separator is detected.

Steps to reproduce:

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