### What problem does this PR solve?
Feat: Reference the output variable of the upstream operator #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Enables the message operator form to reference the data defined by
the begin operator #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Construct RetrievalForm with original fields #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Use shadcn-ui to build GenerateForm. #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Wrap DynamicVariableForm with Collapsible. #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Add DynamicVariableForm with shadcn-ui. #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Add FormDrawer to agent page. #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
