Explore indicating the active agent note in the UI

[benvinegar]

This was generated using GPT 5.5

Summary

Explore a UI treatment that clearly indicates which agent note is active when cycling between notes with { / }.

Context

Hunk supports hunk-specific agent notes and keyboard navigation between them. When there are multiple notes visible or nearby, the active note should be easier to identify spatially in the review stream.

Things to explore

• A subtle active-note highlight, accent border, marker, or icon.
• Ensuring the indication works in both split and stack layouts.
• Keeping the treatment restrained so it does not compete with code diff highlighting.
• Preserving keyboard/mouse parity and existing note navigation behavior.

Acceptance direction

• Cycling notes with { / } makes the newly active note visually obvious.
• The active state remains accessible in common terminal themes and widths.
• The behavior is covered by an appropriate UI/PTY test if implemented.