Output is piped through a pager when it exceeds terminal height — same behavior as git log.

• Activates only when stdout is a TTY and output line count > terminal height
• Uses $PAGER if set, otherwise less -R (preserves ANSI colors)
• Falls back to direct print if the pager fails to spawn
• Ignores broken pipe (user quit pager early — intentional)
• PAGER=cat or piping (blog | cat) disables it
• No new dependencies (uses std::process for pager, terminal_size is already present)

Files changed

Testing

No integration test (requires TTY). Falls back gracefully in piped/test contexts. All existing tests pass.

Split from #166 per review feedback.