chat: migrate functionary_v3_2 to modular PEG parser
Move Functionary v3.2 tool call parsing to
common/chat-syntax/functionary-v3-2.cpp.
Uses native PEG parser for format:
>>>all\ntext>>>fn1\n{...}>>>fn2\n{...}
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
