Feature: persistent project-level theme/color setting in settings.json

Problem

/color purple only sets the session color for the current session. There's no way to persist a color/theme per project so it auto-applies on every session start.

When working across multiple projects, visual differentiation via color helps immediately identify which project you're in. Having to type /color purple at the start of every session is friction.

Proposed Solution

Add a theme or color key to the settings.json schema:

{
  "theme": "purple"
}

This would be supported in all three settings files:

• ~/.claude/settings.json (global default color)
• .claude/settings.json (project-level, shared with team)
• .claude/settings.local.json (personal project override)

The color would auto-apply when a session starts in that project directory.

Alternatives Considered

• SessionStart hook: Hooks run shell commands and can't invoke internal UI commands like /color
• CLAUDE.md instruction: Can remind Claude to suggest it but can't auto-apply
• Manual /color each session: Current workaround, works but adds friction

Use Case

I work on multiple projects and use purple for my main project (Sophie's Trophies). Being able to set this once in .claude/settings.json and have it persist would save a small but repeated step every session.