feat(agentflow): optional cavasActions to allow additional buttons next to validate (#6224)

* feat(agentflow): optional cavasActions to allow additional buttons next to validate

- Updated Agentflow component to support canvasActions prop for rendering additional action buttons in the canvas overlay.
- Enhanced type definitions to include canvasActions in AgentflowProps.
- Added tests to verify the rendering of canvasActions in the Agentflow component.
- Added a new example  demonstrating custom FABs alongside the validation button.

* update jsdoc to match actual implementation