Auto-assign session colors when multiple sessions run in the same project

Feature Request

When running multiple Claude Code sessions in the same project directory, it would be useful for sessions to automatically receive distinct colors so they're visually distinguishable without manual /color setup each time.

Current behaviour

Colours are manual and per-session only via /color <name>. When spinning up 2–3 sessions in the same project (e.g. feature work + bugfix + research), you have to manually assign a colour to each one.

Proposed behaviour

Auto-rotate through available colours (red, blue, green, yellow, purple, orange, pink, cyan) when a new session starts and other sessions are already active in the same project directory. The auto-assigned colour could be overridden with /color as usual.

Why this helps

• Multiple parallel sessions in the same repo is a common workflow (especially with /worktree)
• Glancing at the colour bar across tmux panes or terminal tabs is the fastest way to orient
• Manual /color assignment is low-effort but easy to forget, and the default is the same for all sessions