common: finish the copy bar at 100%

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

common.nix

@@ -29,6 +29,7 @@ let
     {
       blocks='########################################'
       drawn=
+      total=0
       while read -r tag rest; do
         case "$tag" in
           A) copy_id=$rest ;;
@@ -36,6 +37,7 @@ let
              printf '%s\n' "$rest" >&2 ;;
           P) set -- $rest
              [ "$1" = "''${copy_id:-}" ] && [ "''${3:-0}" -gt 0 ] || continue
+             total=$3
              pct=$(( $2 * 100 / $3 ))
              printf '\r[%-40s] %3d%%  %d/%d paths' \
                "''${blocks:0:$(( pct * 40 / 100 ))}" "$pct" "$2" "$3"
@@ -45,7 +47,14 @@ let
       # `if`, not `[ … ] && …`: with nothing to copy the bar never draws, and a
       # bare test as the last statement would exit 1 and break the caller's
       # && chain. A real copy failure still surfaces via the caller's pipefail.
-      if [ -n "$drawn" ]; then printf '\n'; fi
+      #
+      # nix stops emitting type-105 results once the last path lands, so the
+      # bar's last live frame is always one path short. Redraw it full on EOF.
+      # An error would have cleared $drawn via the M branch first, so this only
+      # fires on a copy that actually finished.
+      if [ -n "$drawn" ]; then
+        printf '\r[%-40s] 100%%  %d/%d paths\n' "$blocks" "$total" "$total"
+      fi
     }
   '';