Image sets: a suffix that ends the number before is a repeat too

"051 - White leather kate054001_1_1.jpg": the index is inside 054001
(set 054, image 001) and _1_1 repeats it, but only a suffix equal to the
whole number before counted as a repeat, so the set kept 054001 and every
image was a release (Duke's threads: 2,791 releases of 3,251 files). A
suffix that the number before ends with is a repeat as well. Both
implementations; tests; fixtures identical.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/unit/release/identity.spec.ts

@@ -234,6 +234,7 @@ test.group('release / par2 names', () => {
       ['keira_s04_l keira_s04_0040_l', 'keira_s04_l keira_s04_'],
       ['IMG_2676', 'IMG_'],
       ['2877-041', '2877-'],
+      ['051 - White leather kate054001_1_1', '051 - White leather kate'],
       ['JimAndJoey Kindly Husband-to-Be', ''],
     ]) assert.equal(imageSet(stem), set, stem)
   })