Add keyboard shortcut to navigate between conversation turns in terminal output

Summary

Add a hotkey (e.g. Ctrl+Up/Ctrl+Down) to jump between conversation turn boundaries in the terminal scrollback, so users can quickly navigate to the start of each assistant response without manually scrolling through tool output and intermediate work.

Problem

When Claude works on a task, the terminal fills with tool calls, file reads, bash output, and other intermediate work before the actual response. Finding where the response starts requires manual scrolling. In long sessions with many turns, this becomes tedious.

Proposed Solution

• Visual separator between turns (a horizontal rule or distinct marker)
• Keyboard shortcut to jump forward/backward between turn boundaries
• Alternatively, a shortcut that scrolls to the first non-tool-output line of the current/previous assistant response

Alternatives Considered

• Terminal native scrollback (no semantic awareness of turns)
• Esc+Esc rewind mode (restores state, does not help with reading output)
• /diff (only shows code changes, not conversation)