[FEATURE] persist/auto-set session color (/color) via settings or hook

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

I run this repo checked out in multiple directories/worktrees to work in parallel Claude Code sessions. /color <name> is great for telling sessions apart visually, but it's session-only — there's no way to make a specific directory always start with a given color. I have to re-run /color pink by hand every time I launch Claude Code from that checkout.

I confirmed there's currently no supported mechanism for this:

• No settings.json key (checked the full schema — no color/sessionColor/promptBarColor field).
• No CLI startup flag (claude --help has nothing color-related; the only --color strings in the binary come from bundled ripgrep/grep, unrelated to the app).
• No hook workaround — SessionStart hooks can only run shell commands or inject text via hookSpecificOutput.additionalContext; they can't invoke slash commands, and /color is a built-in local-jsx command, not something scriptable from outside.

Proposed Solution

Either of these would solve it:

1. A sessionColor (or similarly named) field in settings.json, resolved the same way other settings are (user → project → local), so a project-local .claude/settings.local.json could pin a color per directory without affecting other checkouts or teammates.
2. A claude --color <name> startup flag, so it could be wrapped in a shell alias/function per directory.

Option 1 seems preferable since it composes naturally with the existing settings-scope model and needs no shell wrapping.

Alternative Solutions

_No response_

Priority

Low - Nice to have

Feature Category

Interactive mode (TUI)

Use Case Example

Anyone running multiple parallel worktrees/checkouts of the same repo and relying on terminal color-coding to distinguish which session/directory they're in.

Additional Context

_No response_