Add --experimental-new-parsers CLI flag for llama-server
Adds a CLI flag to enable experimental PEG parsers:
- `--experimental-new-parsers` flag for llama-server
- `LLAMA_ARG_EXPERIMENTAL_NEW_PARSERS` environment variable
- Propagated through oaicompat_parser_options to chat template inputs
Also adds scripts/test-chat-parsers.sh for CI validation of both
legacy and new parser paths.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
