Add Spring Festival workflows: spring_text_image, spring_text_image_EN, and spring_3d
spring_text_image – Chinese prompt version of a multi-agent content pipeline (planner → copywriter → editor → poster generation).
spring_text_image_EN – English prompt version of the same workflow structure, adapted for broader international usage.
spring_3d – A simplified 3D scene generation workflow that outputs Blender Python scripts for Spring Festival themed scenes.
- Remove invalid 'version' field
- Restructure to match DevAll YAML schema (graph at top level)
- Move start/end nodes to end of graph block
- Validation now passes: 'Workflow OK. Design is valid.'
- Merge demo_loop_timer.yaml and demo_loop_timer_passthrough.yaml into single comprehensive demo
- Create dual-branch workflow demonstrating both standard and passthrough modes side-by-side
- Increase duration from 5 seconds to 2 minutes for better demonstration
- Update YAML_FORMAT_QUICK_GUIDE.md with detailed mode explanations and demo reference
- Update tasks.md in add-loop-timer proposal to reflect demo improvements
- Remove duplicate demo_loop_timer_passthrough.yaml file
- Add LoopTimerConfig with duration units support (seconds/minutes/hours)
- Implement LoopTimerNodeExecutor with standard and passthrough modes
- Register loop_timer node type in builtin_nodes.py
- Update documentation (execution_logic.md, YAML_FORMAT_QUICK_GUIDE.md)
- Add demo workflows for both modes
Closes: add-loop-timer change proposal
