[Feature Request] Add configurable or random session color at startup

Bug Description
▎ Feature request: random / configurable session color at startup

▎ Currently /color can only be set manually per session. It would be useful to have:

▎ 1. A settings.json option like sessionColor: "random" (or a fixed color) to auto-apply at session start, or
▎ 2. A CLI flag claude --color=random|red|blue|..., or
▎ 3. Allowing SessionStart hooks to set the session color via a new hookSpecificOutput.sessionColor field.

▎ Use case: when running multiple Claude Code sessions in parallel (different terminals/projects), a unique random color per session makes it instantly obvious which
terminal belongs to which session.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.92
• Feedback ID: 42684eec-b037-4ddc-a033-932c12d02dbe

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/christophwerker/.local/share/claude/versions/2.1.92 (expected in multi-process scenarios)\n    at im_ (/$bunfs/root/src/entrypoints/cli.js:1884:2153)\n    at An6 (/$bunfs/root/src/entrypoints/cli.js:1884:1233)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-04T23:43:44.527Z"}]