Replace tee with _snaplog_tee shell function that writes each line
unbuffered to three destinations: snapshot log, application log file,
and stderr (which the TUI captures for live display). This fixes the
issue where rsync file-by-file output was invisible in both the Logs
screen and the Running Tasks view due to pipe buffering.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Save log, rsync_error, summary, and index files into each snapshot
directory after backup. Rsync/rclone output is captured via tee during
transfer so the TUI still shows live output while logging to disk.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
