Setting to keep the desktop composer resting as a one-line pill

[Conte777]

Problem

On web and desktop, the composer rests into a one-line pill only while I scroll the conversation up. As soon as the timeline reaches its end again — for example, when the agent finishes a turn — the composer expands back to the full-height layout with the controls row inside it.

I prefer the resting layout all the time. It leaves more of the conversation visible, and I can type in it without problems. Today the only choice is Collapse composer on scroll on or off (composerCollapseOnScroll); there is no way to make the resting layout the default.

Proposal

Turn Collapse composer on scroll into a three-way choice:

• On scroll — today's default, unchanged
• Always — the composer stays in the resting layout; scrolling to the end and sending a message do not expand it
• Never — today's switch turned off

The resting layout and its transition already exist (shouldUseRestingComposerLayout, useComposerRestingTransition). The new option only changes when the composer enters and leaves that layout, so it should be a client-only change. A stored boolean decodes as true → On scroll, false → Never.

Open question

What should happen when a draft grows past one line in Always mode? Growing the pill up to a max height seems right to me, but I'm open to expanding the composer while the draft is multi-line.

Related

• feat(web): let users turn off composer collapse on blur and scroll #9469 added the collapse settings; fix(web): stop collapsing the composer when it loses focus #10437 removed the blur trigger and kept the scroll switch.
• [Feature]: Collapsible composer so the thread is readable while a question or approval is pending #6849 asks for a manual collapse toggle while a question or approval is pending.

Surfaces

Web and desktop. Mobile keeps its own keyboard-driven collapse.