Per-speaker text color customization (user vs. assistant messages)

Currently there's no way to set distinct text colors for user messages vs. Claude's messages in the terminal UI — color is inherited entirely from the terminal emulator's profile, with no per-role granularity exposed by Claude Code itself.

Feature request: Add a settings.json option (or a /theme-style picker) to let users assign a custom color to their own messages and a separate color to Claude's messages, persisted across sessions.

Use case: Makes it easier to visually scan long conversation history and quickly distinguish "what I said" from "what Claude said" at a glance.