Pending ladder: a hash-named release of several pieces gets a lone target

The edge gave an unnamed release a "lone" probe target only when it had
exactly one file, so a release of several random-named pieces (Bob's,
1.55M rows in five groups) reached the pending store with no target at
all: never claimed, never named by a twin, its class never learned.
candidates_of now takes the first random-named file when there is no
par2, archive or 7z volume. The batch store writes a finished release
without a target as exhausted instead of waiting, and leaves it out of
its class's waiting count. LOG.md (140).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/functional/batch_store.spec.ts

@@ -538,6 +538,38 @@ test.group('BatchStore', (group) => {
     assert.include(await db.from('pending_releases').firstOrFail(), { files: 2, segments: '5' })
   })
 
+  test('a finished unnamed release without a probe target is exhausted at once, not waiting', async ({
+    assert,
+  }) => {
+    const { rangeId, nodeId } = await rangeIn(GROUP, 1)
+    // Two hash-named pieces: the edge gives the first a lone target; without one the ladder could never claim it.
+    const batch = batchOf(GROUP, 1, [
+      ...upload(
+        10,
+        '9e7fc2741cdd450287aff2733ca4c193',
+        4,
+        'b3a75d234aa73891e78a70fc1f5496b1 [1/2]',
+        '2026-10-05T10:00:00Z'
+      ),
+      ...upload(
+        20,
+        'c5ebdd5487f5b132c76e8d5c2572e560',
+        4,
+        'b3a75d234aa73891e78a70fc1f5496b1 [2/2]',
+        '2026-10-05T10:01:00Z'
+      ),
+    ])
+    assert.lengthOf(batch.releases, 1)
+    assert.isFalse(batch.releases[0].readable)
+    const stored = await BatchStore.store(rangeId, nodeId, { ...batch, candidates: [] })
+    assert.include(stored, { releases: 1, newReleases: 0, candidates: 0, pending: 1 })
+    const pending = await db.from('pending_releases').firstOrFail()
+    assert.include(pending, { files: 2, finished: true, status: 3 })
+    assert.deepEqual(pending.candidates, [])
+    const klass = await db.from('pending_classes').firstOrFail()
+    assert.include(klass, { waiting: 0 })
+  })
+
   test("an album's members stay findable by their own names (release_texts kind member)", async ({
     assert,
   }) => {