add pagetest.sh: generate a page-break diagnostic printout

Numbered, fixed-width lines let us read a printer's actual page length
and line width limits straight off the paper, instead of guessing them
from A4 geometry - needed to nail down the real constants for the
PRINTER_A4 landscape math.

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

pagetest.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+#
+# Generates a page-break diagnostic file: numbered lines padded with '#' to
+# a fixed width, so you can see exactly where a printer's real page length
+# and line width limits are instead of guessing from paper geometry.
+#
+# Usage: ./pagetest.sh [width] [lines]
+#   width - characters per line, including the "NNN " prefix (default 64)
+#   lines - number of lines to generate (default 100)
+#
+# Print the result with PRINTER_A4=false in printer.conf (no rotation), so
+# the line numbers read straight off the page:
+#   ./txt2printr.sh pagetest.txt
+
+dir="$(dirname "$0")"
+width="${1:-64}"
+lines="${2:-100}"
+outfile="$dir/pagetest.txt"
+
+awk -v width="$width" -v lines="$lines" '
+    BEGIN {
+        for (i = 1; i <= lines; i++) {
+            prefix = sprintf("%03d ", i)
+            fill = width - length(prefix)
+            if (fill < 0) fill = 0
+            line = prefix
+            for (j = 0; j < fill; j++) line = line "#"
+            print line
+        }
+    }
+' > "$outfile"
+
+echo "Wrote $lines lines x $width chars to $outfile"
+echo "Print it with: PRINTER_DEV=/dev/lp0 \"$dir/txt2printr.sh\" \"$outfile\""