Cap the METEOR fragmentation penalty so scores stay in [0, 1] (#210)

_calculate_fragmentation_penalty divides chunk counts taken over the full token
sequence (repeats included) by the number of distinct matched words, so the
ratio can exceed 1 and the METEOR score can go negative. Cap the penalty at 1.
Only scores that were negative change (they become 0). Also re-scores the one
negative cached value (claude-3-haiku, NarrativeQA_4102).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: yl231