Patches @blocknote/core SuggestionMenu plugin to fix multi-character
trigger detection. The original code used textBetween(from - len, from)
which included text before the trigger, causing [[ to only match at
line starts. Fixed to textBetween(from - (len - 1), from).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>