Add action 'Run Scene Beat'

[CWolfs]

Add a combined action for common conversation scene staging.

At the moment, common scene setup can require several separate actions for fades, viewscreen changes, camera lock, character visibility, and later animation support. This is powerful, but not very friendly when building repeatable scene beats.

For this change:

• Add an action called Run Scene Beat
• Support common scene setup in one operation:
  • Fade mode
  • Camera hard lock target
  • Viewscreen image or reset
  • Characters to show
  • Characters to hide
  • Optional animation id when animation support exists
• Keep each field optional so the action can be used for small beats as well as larger transitions
• Apply the requested steps in a predictable order
• Log each step clearly for troubleshooting
• Add the ConverseTek operation definition JSON
• Document how this differs from using the individual lower-level actions directly