[FEATURE] Persistent per-project session color for multi-window identification

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

When working on multiple projects simultaneously with Claude Code open in separate terminal windows, there's no persistent visual way to tell which window belongs to which project. The /color command exists but only applies to the current session — it resets every time you start a new session.

This makes it easy to type into the wrong window, especially when switching between 2–3 projects quickly.

Proposed Solution

Allow setting a persistent default session color per project via .claude/settings.local.json or a similar project-level config:

{
  "sessionColor": "blue"
}

When Claude Code starts in that project directory, it automatically applies the configured color — no need to run /color manually each time.

Alternative Solutions

• A SessionStart hook that runs /color blue — but hooks don't support slash commands
• Adding /color blue to CLAUDE.md as an instruction — but Claude can't execute slash commands
• Manually running /color at the start of every session — current workaround, but tedious

Priority

Medium - Quality of life improvement

Feature Category

Interactive mode (TUI)

Use Case Example

I work on 3 different microservices (app-sso, app-service, app-admin) with Claude Code open in separate terminals. Assigning each project a persistent color (blue, green, orange) would let me instantly identify which terminal is which at a glance.

Additional Context

Related to #11145 (rename VS Code tabs) which addresses a similar "identify which session is which" problem for the VS Code extension. This request is for the CLI/terminal experience.