Reformat progress lines and prune output

Progress lines now use the form:
  ..., <subject> elapsed: <dur>, <subject> ETA: <time> (est remain <dur>).

ui.Time formats same-day times as HH:MM:SS and other-day times as
YYYY-MM-DD HH:MM:SS, with no timezone suffix (local time is implied).

The local-index-database prune complete line now shows remaining
counts for each category:
  ... 1 incomplete snapshots removed (3 remain), 3783 orphaned files
  removed (42 remain), ...

internal/ui/ui_test.go

@@ -72,6 +72,16 @@ func TestValueFormattersPlain(t *testing.T) {
 	if got := w.Percent(12.34); got != "12.3%" {
 		t.Errorf("Percent: got %q", got)
 	}
+
+	// Time format: today → HH:MM:SS, other day → YYYY-MM-DD HH:MM:SS.
+	today := time.Date(time.Now().Year(), time.Now().Month(), time.Now().Day(), 14, 30, 45, 0, time.Local)
+	if got := w.Time(today); got != "14:30:45" {
+		t.Errorf("Time today: got %q, want 14:30:45", got)
+	}
+	other := time.Date(2030, 1, 2, 3, 4, 5, 0, time.Local)
+	if got := w.Time(other); got != "2030-01-02 03:04:05" {
+		t.Errorf("Time other day: got %q", got)
+	}
 }
 
 func TestValueFormattersColored(t *testing.T) {