fix: make PEG mappers lazy to avoid spurious tool calls during backtracking
- Make common_chat_peg_native_mapper and common_chat_peg_constructed_mapper_func
defer tool call creation to TOOL_NAME instead of TOOL_OPEN
- This fixes parallel-tool-calls failures in DeepSeek R1/V3.1 and other templates
- Also includes Generic parser fixes for tool_calls | response format
- Improves needle streaming test pass rate from 16/22 to 20/22 templates
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>