Update drag-and-drop rx.foreach example to use key prop

[masenf]

No description provided.

[greptile-apps]

Greptile Summary

This PR improves the drag-and-drop documentation by clarifying why key props matter in rx.foreach and updating the example accordingly.

• Adds a brief explanation that a stable item identifier should be passed as the key prop to the outermost component rendered by rx.foreach, so React can track item identity during list reordering.
• Updates the droppable_list example to call draggable_list_item(item=item, key=item.id) instead of draggable_list_item(item=item), aligning the demo code with the new guidance.

Confidence Score: 5/5

Documentation-only change; no runtime code is modified.

The change adds a short paragraph of guidance and threads key=item.id into the memoized component call, which is the correct pattern for stable list rendering in Reflex. The updated example matches the new prose, and the ListItem.id field already exists in the dataclass, so the key expression is valid. No logic, APIs, or side effects are touched.

No files require special attention.

Important Files Changed

Filename	Overview
docs/enterprise/drag-and-drop.md	Adds explanatory prose about the key prop requirement for rx.foreach and updates the draggable list example to pass key=item.id to the memoized component.

_{Reviews (1): Last reviewed commit: "Update drag-and-drop rx.foreach example ..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing masenf/enterprise-docs-dnd (7c3a8c3) with main (f232cf4)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩