Under a constant subject: an upload's random volume stem, and an image's set head

- "[ TOWN ] [ www town ag ] [ TV ] … "Z3mMTMPsoT4ikE_Di3fKnNF21.part01.rar"",
  "….vol4+4.par2": the subject and the total were the key, so every upload of
  a total was one release (2,338 files for 20; also partner-of-ssl-news,
  brothers-of-usenet). A random stem (no dots or spaces) on a volume file
  joins the subject key; a scene name doesn't, so its nfo stays.
- "Molly Set [i/50] "mo103x003.jpg"": every set of 50 was one. An image's
  name up to its first number, when another follows, joins the key.

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

tests/unit/release/identity.spec.ts

@@ -443,6 +443,20 @@ test.group('release / par2 names', () => {
     assert.notEqual(r('022', '457', "r86_022 - Gwen Guthrie - Ain't Nothing Going on but the Rent.mp3").key, r('022', '333', "r98_333 - Jellie - Roller Coaster.mp3").key)
   })
 
+  test("under a constant tag an upload's random stem, and an image's set, bound the subject", ({ assert }) => {
+    const id = (subject: string, name: string) => releaseIdentity({ poster: 'Kim <Jong-Un@town.ag>', subject, name, weak: false })!
+    const town = (i: string, n: string) => id(`[ TOWN ] [ www.town.ag ] [ TV ] [${i}/20] - "${n}" yEnc`, n)
+    assert.equal(town('01', 'Z3mMTMPsoT4ikE_Di3fKnNF21.part01.rar').key, town('18', 'Z3mMTMPsoT4ikE_Di3fKnNF21.vol4+4.par2').key)
+    assert.equal(town('01', 'Z3mMTMPsoT4ikE_Di3fKnNF21.part01.rar').name, town('01', 'i3DpbaTUJT4L6V48fEBdbVV46.part01.rar').name)
+    assert.notEqual(town('01', 'Z3mMTMPsoT4ikE_Di3fKnNF21.part01.rar').key, town('01', 'i3DpbaTUJT4L6V48fEBdbVV46.part01.rar').key)
+    // A scene name keeps the subject's key, so its nfo stays with it.
+    const show = (i: string, n: string) => id(`Some.Show.S01E01 [${i}/20] - "${n}" yEnc`, n)
+    assert.equal(show('01', 'The.Big.Bang.Theory.S01E01.part01.rar').key, show('20', 'The.Big.Bang.Theory.S01E01.nfo').key)
+    const molly = (i: string, n: string) => id(`Molly Set [${i}/50] - "${n}" yEnc`, n)
+    assert.equal(molly('01', 'mo103x003.jpg').key, molly('02', 'mo103x004.jpg').key)
+    assert.notEqual(molly('01', 'mo103x003.jpg').key, molly('01', 'mop120x032.jpg').key)
+  })
+
   test('an image without words around it is keyed by its set', ({ assert }) => {
     const id = (name: string, counter: string) => releaseIdentity({ poster: 'p', subject: `##[ "${name}" (${counter})`, name, weak: false })!
     assert.equal(id('diana-040-001.jpg', '01/68').key, id('diana-040-002.jpg', '02/68').key)