Collapsible output sections per type (thinking, command output, tool calls, messages) with colour-coded type indicators

[berrat]

Describe the feature or problem you'd like to solve

During a complex agent session, the scrollback fills up rapidly with a mix of very different content types — reasoning/thinking blocks, tool/command output, background task results, and the agent's final message. These are all rendered as a flat, undifferentiated stream. There is no way to collapse a 200-line command output you've already read, fold away a long thinking block, or visually distinguish at a glance what type of content each section is. Navigating a long session becomes increasingly unwieldy as output accumulates.

Proposed solution

Make each discrete output section independently collapsible, with colour-coded type indicators so the nature of each block is immediately recognisable.

Collapsible sections — toggle individually or all at once:

Section type	Collapse behaviour
💭 Thinking / reasoning	Fold to a single summary line (e.g. 💭 Thinking [~340 tokens] ▶ expand)
⚙ Tool call / command output	Fold to tool name + exit code (e.g. ⚙ pwsh ✔ ▶ expand)
🤖 Background / worker task	Fold to agent type + status (e.g. 🤖 explore ✔ done ▶ expand)
💬 Agent message	Collapsible but shown expanded by default

Keyboard controls:

• ← / → (or z) on a focused section — collapse / expand that section
• Ctrl+← / Ctrl+→ — collapse / expand all sections of that type at once
• Ctrl+Shift+← — collapse everything in the scrollback (clean slate view)
• Ctrl+Shift+→ — expand everything

Colour-coded leading indicators (respects terminal theme / AUTO palette):

💭  [dim purple]   Thinking
⚙   [dim yellow]   Tool call / command
🤖  [dim cyan]     Background task / worker agent
💬  [white]        Agent message
✖   [red]          Error / failure

Collapsed sections render as a single muted line with a ▶ expand arrow. Expanded sections show the ▼ arrow. Users who prefer a minimal UI can set "collapsibleOutput": false in config.json to revert to the current flat rendering.

Example prompts or workflows

1. Agent produces a 300-line npm test output. User reads it, then collapses it with ← — one line remains, scrollback is clean.
2. User wants to hide all thinking blocks for the session — Ctrl+← on any thinking block collapses every thinking section at once.
3. User glances at the colour indicators to quickly scan which turns involved tool calls vs. pure reasoning vs. final answers — without reading a single word.
4. User runs Ctrl+Shift+← to collapse all output after a long session, then selectively re-expands only the sections they want to revisit.
5. User disables the feature entirely via config — output renders exactly as it does today.

Additional context

• OS: Windows 11 Pro (Build 26200 / 24H2)
• Shell: PowerShell 7.5.4
• Copilot CLI: 0.0.420 (win32-x64)
• Thinking blocks are already visually separated in some form in the current UI — this extends that into full interactivity.
• The colour indicator system should integrate with the existing AUTO theme so colours adapt correctly to any terminal colour scheme.
• This is a significant UX improvement for long or complex sessions where the scrollback becomes the primary navigation challenge.