fuzz-nightly: lex target crashed

[github-actions]

Nightly fuzz of the lex target failed.

Run: https://github.com/devrelaicom/compactp/actions/runs/26642609467
Artifacts: crash inputs were uploaded as workflow artifacts (look for fuzz-crashes-lex-26642609467).

Next steps:

1. Download the crash artifact from the workflow run.
2. Reproduce locally with scripts/fuzz.sh --target lex --duration 1 or directly via cat fuzz/artifacts/lex/<input> | cargo +nightly fuzz run lex.
3. Fix and add a reduced reproducer as a unit test in the relevant grammar module.