Allow customization of spinner animation frames via settings

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

We can customize spinnerVerbs (the text) and spinnerTipsOverride (the tips), but there's no way to customize the actual spinner animation characters — the braille/ASCII frames that cycle while Claude is thinking.

The animation is currently hardcoded. Users who invest in personalizing their Claude Code experience (custom verbs, tips, themes) have no way to change the most visually prominent part of the spinner.

Proposed Solution

Add a spinnerFrames setting to settings.json, following the same pattern as spinnerVerbs:

{
  "spinnerFrames": {
    "mode": "replace",
    "frames": ["⠁", "⠈", "⠐", "⠠", "⢀", "⡀", "⠄", "⠂"]
  }
}

• mode: "replace" — use only the provided frames
• mode: "append" — add frames to the default set (less useful here, but consistent with spinnerVerbs)
• frames — array of single characters or short strings to cycle through

Optionally, a spinnerFrameRate (ms per frame) setting would pair well with this, and also address #33349.

Example: Breathing Circle Animation

A braille "breathing circle" where a dot orbits clockwise, gaining a trailing dot each loop until 5 are lit, then reversing counterclockwise back down to 1 — creating an inhale/exhale effect:

CW build-up:
1 dot:  ⠁ ⠈ ⠐ ⠠ ⢀ ⡀ ⠄ ⠂
2 dots: ⠃ ⠉ ⠘ ⠰ ⢠ ⣀ ⡄ ⠆
3 dots: ⠇ ⠋ ⠙ ⠸ ⢰ ⣠ ⣄ ⡆
4 dots: ⡇ ⠏ ⠛ ⠹ ⢸ ⣰ ⣤ ⣆
5 dots: ⣇ ⡏ ⠟ ⠻ ⢹ ⣸ ⣴ ⣦

CCW wind-down:
4 dots: ⠛ ⠏ ⡇ ⣆ ⣤ ⣰ ⢸ ⠹
3 dots: ⠋ ⠇ ⡆ ⣄ ⣠ ⢰ ⠸ ⠙
2 dots: ⠃ ⠆ ⡄ ⣀ ⢠ ⠰ ⠘ ⠉
1 dot:  ⠂ ⠄ ⡀ ⢀ ⠠ ⠐ ⠈ ⠁

This kind of animation is impossible with the current hardcoded frames but trivial to support with a spinnerFrames array.

Alternative Solutions

_No response_

Priority

Low - Nice to have

Feature Category

Configuration and settings

Use Case Example

Users who customize their terminal environment want spinner animations that match their aesthetic — minimal single-dot orbits, breathing patterns, or domain-specific animations.

Additional Context

Related: #29338 (spinner parity in Co-work), #33349 (spinner refresh rate)