Refactored Tool Execution Architecture

What changed: Internal tool execution system migrated from function-based approach to a class-based queue system with better concurrent execution support.

Technical details:

• New Qr1 class manages tool execution queue with status tracking ("queued" → "executing" → "completed" → "yielded")
• Intelligent concurrency: Tools marked as concurrency-safe can execute in parallel, while non-concurrent-safe tools block subsequent processing
• Feature-flag controlled: Uses tengu_streaming_tool_execution flag to gradually roll out new architecture
• Backward compatible: Falls back to renamed legacy functions (Ev5() at line 429788) when feature flag is disabled

User impact:

• Better responsiveness when Claude uses multiple tools simultaneously
• More efficient parallel processing of independent operations
• Improved result streaming as tools complete