Fix GBNF grammar generation for optional repetitions and lazy mode
- Fix optional (min=0, max=1) repetition wrapping to avoid double-wrapping
- Format choice/sequence wrapped in optional as "(...)?", not "((...))?"
- Add fallback for lazy mode when no trigger rules are found
- If lazy mode requested but no trigger rules exist, fall back to full grammar
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>