Fix layout visual bugs

[engkareeem]

Fix panel overflow and scroll issues

Problems

1. Horizontal overflow in panels
Input fields caused panels to grow horizontally beyond their intended width. The root cause was ScrollArea's internal viewport div rendering with display: table, which made the container size to its content instead of constraining it.

2. Non-functional scroll in the AI workflow generation panel
The FloatingWorkflowGen panel uses absolute positioning, which caused ScrollArea to not scroll correctly — content would overflow without a scrollable region.

3. Parallel Agent instruction text overflowing the node card
The shared instructions preview on the Parallel Agent node overflowed outside the card boundary. A JS-based character truncation helper was being used, which didn't prevent layout breakage.

---

Fixes

• scroll-area.tsx — Force the internal viewport div to display: block, preventing horizontal expansion to fit content.
• floating-workflow-gen.tsx — Replace ScrollArea with a native div using overflow-y-auto, which works correctly regardless of positioning context.
• parallel-agent/node.tsx — Replace JS truncate() with CSS truncate (overflow: hidden; text-overflow: ellipsis; white-space: nowrap), clipping the text cleanly at the card edge.