feat(agent): similar to the start node of workflow, agent variables also support drag-and-drop

[yangzheli]

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Summary

fix #26507
refer to #22150

Screenshots

Before	After

agent.mov

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[gemini-code-assist]

Summary of Changes

Hello @yangzheli, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the usability of agent variable management by implementing drag-and-drop reordering. This feature provides a more intuitive way for users to organize their variables, aligning the experience with similar functionalities found in workflow start nodes and contributing to a more flexible and user-friendly configuration interface.

Highlights

• Drag-and-Drop for Agent Variables: Introduced drag-and-drop functionality for agent variables, allowing users to reorder them, similar to the existing feature for workflow start nodes. This enhances the user experience for managing variable configurations.
• Integration of ReactSortable: The ReactSortable library has been integrated into the ConfigVar component to enable the reordering of variable items through drag-and-drop gestures.
• Unique ID Generation for Variables: Each agent variable is now assigned a unique ID using uuid4 to facilitate stable and efficient reordering within the ReactSortable component.
• Visual Drag Handle: A draggable icon (RiDraggable) has been added to VarItem components, which appears on hover, providing a clear visual cue for the drag-and-drop capability.
• Conditional Dragging: Dragging is conditionally enabled only when the variable list is not in a readonly state and contains more than one item, preventing unnecessary drag handles in single-item or locked configurations.

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[gemini-code-assist]

Code Review

This pull request introduces drag-and-drop functionality for agent variables, which is a great usability improvement. The implementation uses react-sortablejs. However, I've found a couple of critical issues in how it's being used in web/app/components/app/configuration/config-var/index.tsx that would lead to incorrect behavior after reordering variables. Specifically, the use of unstable IDs for sortable items and an incorrect rendering loop will cause event handlers for editing or removing variables to target the wrong items. A similar pre-existing issue was identified in web/app/components/workflow/nodes/start/components/var-list.tsx, which was refactored in this PR. I've provided detailed comments and code suggestions to address these critical problems.

[yangzheli]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces drag-and-drop reordering for agent variables, making it consistent with the behavior of start node variables in a workflow. The implementation uses react-sortablejs and includes related UI changes for the drag handle. Additionally, there are some beneficial refactorings in the start node's variable list component, such as using more stable keys for list items.

My review focuses on the choice of keys for the sortable list items. While the change from using an index to a variable name as a key is an improvement for reordering, it can cause issues when the variable name itself is editable, which appears to be the case. I've provided two comments with suggestions on how to address this to ensure stable component identity during edits.