Display per-message timestamps in chat/session view

Feature request

Currently, messages in a Claude Code session (interactive terminal UI) don't show a timestamp. It would be helpful to see when each message/turn happened, especially in long-running or resumed sessions.

Motivation

• Useful for tracking how long a task took, or when a particular exchange happened in a multi-hour/multi-day session.
• Session JSONL logs under ~/.claude/projects/<project-hash>/ already store a timestamp field per message record — the data exists, it's just not surfaced in the terminal display. So this seems like it would mainly be a UI addition rather than a new data-tracking feature.

Suggestion

Show a timestamp (or relative time, e.g. "2m ago") next to each user/assistant message in the terminal transcript, possibly toggleable via a setting for users who prefer a cleaner view.