Add per-message timestamps to conversation UI

Feature Request

Add a timestamp (HH:MM:SS or configurable format) to each message in the Claude Code CLI conversation view — both user submissions and assistant responses.

Why

• Sessions can run for hours. There's no way to tell when something happened.
• Every comparable tool does this: Slack, Discord, iTerm2, VS Code terminal, IRC, even script from 1979.
• Useful for debugging, context ("how long ago did that build run?"), and reviewing session history.

Suggested implementation

A setting like "showTimestamps": true in settings.json that prepends a gray timestamp to each message:

[14:32:05] > commit and push
[14:32:08] Pushed. e77eea8 is live on main.
[14:45:12] > is there a way to have timestamps...

Could also be a CLI flag (--timestamps) or always-on with a toggle.