Add adaptive preprocessing escalation and single-receipt test scripts

Preprocessing now tries progressively heavier variants per receipt
(plain -> high-pass -> edge-enhance -> both), stopping as soon as a
cheap LLM-free arithmetic check on the OCR text looks plausible, so
the extra processing only applies to receipts that need it. A flat
version of the same heavier processing regressed the full batch by
helping hard receipts but hurting easy ones; the adaptive version
improves date-matching 37/52 -> 40/52 with no regression (see
testing/2026_10_04_gimp_highpass_nlfilter_experiment.md).

Also adds test_ocr.sh and test_single.sh for checking a single
receipt's OCR text or full pipeline result without a batch run.

test_ocr.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+# Test-only tool: runs preprocessing + OCR (1_preprocess_image.sh,
+# 2_ocr_image.sh - variant 0/baseline only, deliberately not
+# 12_adaptive_preprocess_ocr.sh) on a single receipt photo and prints the
+# raw OCR text to stdout - no LLM extraction step, no ground-truth
+# comparison, and no files left behind (unlike test_single.sh/
+# test_batch.sh, which persist scratch/result directories and go through
+# the real adaptive pipeline). Useful for quickly checking what Tesseract
+# actually reads off one specific preprocessing variant in isolation -
+# e.g. while iterating on tooling-container/src/preprocess.py - without
+# the adaptive step's variant selection in the way, waiting on the LLM
+# call, or needing ground truth.
+#
+# Usage: ./test_ocr.sh -in <photo.jpg>
+set -euo pipefail
+
+cd "$(dirname "${BASH_SOURCE[0]}")"
+
+fail() { echo "FAIL: $*" >&2; exit 1; }
+
+IN_PATH=""
+while [ $# -gt 0 ]; do
+    case "$1" in
+        -in) IN_PATH="${2:-}"; shift 2 ;;
+        *) fail "unknown argument: $1" ;;
+    esac
+done
+[ -n "$IN_PATH" ] || fail "usage: $0 -in <photo.jpg>"
+[ -f "$IN_PATH" ] || fail "input file not found: $IN_PATH"
+
+SCRATCH_DIR="$(mktemp -d)"
+trap 'rm -rf "$SCRATCH_DIR"' EXIT
+
+./1_preprocess_image.sh -in "$IN_PATH" -out "$SCRATCH_DIR" >/dev/null
+./2_ocr_image.sh -in "$SCRATCH_DIR/03_final.png" -out "$SCRATCH_DIR" >/dev/null
+
+cat "$SCRATCH_DIR/ocr.txt"