Terminal UI: collapsible sections and section navigation

Summary

The terminal UI shows all tool calls (Bash, Read, Edit, etc.) inline with assistant messages, making long conversations hard to scan. The mobile/remote-control interface already collapses tool outputs into single-line summaries that expand on click — bringing similar functionality to the terminal would significantly improve readability.

Requested Features

1. Collapsible tool output sections

• Tool call outputs (Bash, Read, Write, Edit, Grep, etc.) should be collapsible to a single summary line by default, expandable with a keypress
• Similar to how the remote-control web interface already handles this
• Ctrl+Shift+B (brief mode) is a step in this direction but is all-or-nothing — per-section control would be much more useful

2. Visual grouping of sections

• Different message types (assistant text, tool calls, tool output, errors) could use distinct background colors or border styling to make them visually distinguishable
• The current colored dots on the left margin are subtle and easy to miss — a colored left border or light background tint would make sections scannable at a glance
• Many modern terminals support 24-bit color and Unicode box-drawing characters, so richer visual grouping is feasible

3. Section navigation keyboard shortcuts

• Jump to next/previous assistant message (skipping over tool calls)
• Jump to next/previous tool call
• Collapse/expand the section under the cursor
• Collapse all / expand all tool outputs

4. Section group operations

• Collapse all tool outputs at once (show only assistant messages)
• Expand all tool outputs at once
• Toggle between "reading mode" (assistant messages only) and "debug mode" (everything visible)

Context

• Brief mode (Ctrl+Shift+B) and transcript toggle (Ctrl+O) help but are binary — they affect everything at once
• The message selector (Esc Esc) allows jumping between messages but doesn't support collapsing or visual grouping
• The remote-control/mobile interface already has collapsible tool sections, so the underlying data model supports this — it's a terminal rendering gap
• Terminal capabilities (24-bit color, box-drawing, Ink's layout engine) should support richer visual grouping

Environment

• Platform: WSL2 (Windows Terminal)
• Claude Code terminal UI