Add use_legacy_parsers feature flag for PEG parser migration
- Add use_legacy_parsers flag to common_chat_templates_inputs and templates_params
- Rename modular parser functions with _peg suffix in chat-parsers/*.cpp
- Add legacy wrapper functions in chat.cpp that route based on flag
- Functions that already used PEG/XML in master delegate directly to _peg versions
(ministral_3, nemotron_v3, minimax_m2, qwen3_coder_xml, kimi_k2, apriel_1_5,
xiaomi_mimo, glm_4_5, seed_oss, function_gemma)
- Default: use_legacy_parsers=false (new PEG parsers)
- When true: uses legacy implementations from master
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
