Expose `prefersReducedMotion` as a runtime toggle (slash command or `/config` entry)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

While Claude Code is running a long tool call, the spinner animation
redraws frequently enough that xterm (and likely other terminals with
default alternate-screen scrollback behavior) interpret the redraw as
active output and auto-scroll the viewport to the bottom whenever the
user scrolls up to review earlier context. The result is that reading
prior output during an active task is essentially impossible without
pausing the session.

Proposed Solution

A runtime way to toggle prefersReducedMotion without editing JSON
and restarting, for example:

• A row in the /config TUI (alongside theme, model, etc.) with

an on/off toggle, or

• A dedicated slash command such as /motion off / /motion on, or
• A keybinding (e.g. a chord in ~/.claude/keybindings.json) that

flips the setting mid-session.

Any of the three would be a meaningful accessibility and
terminal-ergonomics improvement, especially for users on classic
xterm, tmux panes with default scroll behavior, and screen-reader
setups where reduced motion is preferable by default.

Alternative Solutions

Setting "prefersReducedMotion": true in ~/.claude/settings.json
disables the spinner. The setting works
well, it is just not discoverable at runtime — users only find it by
asking, reading the schema, or browsing issues. Restarting the CLI
after editing a static settings file is also friction when the user
is only trying to scroll through history once.

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

Example scenario:

1. I use claude code CLI in xterm.
2. It's working to resolve a prompt, takes ages. I want to review earlier discussion in the terminal but I cant scroll up because it keeps rendering new spinner characters at the bottom.
3. I give up trying to scroll.

Additional Context

• Claude Code CLI (any recent version)
• Linux, xterm (reproducible)
• Likely reproducible on any terminal that snaps-to-bottom on output