Rebuild: fragments only for files an edge cut; lone random articles are per-article

Measured on two neighbouring boneless ranges (merging their fragments):
- 99.8% of fragment files were single articles of a random-named
  'file' of >100 parts: a random subject per article, which never
  completes from headers. They now count as per-article.
- A file is kept as a fragment when its first part seen is above 1 and
  comes within the start window (the idle window: uploads in busy groups
  spread over minutes, and a 50k-article edge zone is ~30 s of boneless),
  or when it was still open at the range's end with later parts missing.
  Anything else missing parts is incomplete and only counted.
Per range: 70,308 → 130 fragment files; merged, 47 of the 48 files met
complete (57,558 segments, ~8% of the range's kept segments).

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

tests/unit/edge/range_indexer.spec.ts

@@ -55,13 +55,22 @@ test.group('edge / RangeIndexer', () => {
     assert.equal(batch.next, 1_000_001)
   })
 
-  test('a file cut off near an edge leaves as fragments, one in the middle is only counted', ({ assert }) => {
+  test('files the edges cut leave as fragments; one missing parts in the middle is only counted', ({ assert }) => {
     const indexer = new RangeIndexer({ group: GROUP, start: 1, end: 1_000_000, rules, edgeArticles: 1000 })
-    indexer.add([...post(5, 'Edge.File.2020.part1.rar', 3).slice(0, 2), ...post(500_000, 'Middle.File.2020.part1.rar', 3).slice(0, 2)], 600_000)
+    indexer.add([
+      // Parts 2–3 right after the start: part 1 is in the previous range.
+      ...post(5, 'Start.Cut.2020.part1.rar', 3).slice(1),
+      // Parts 1–2 seen, part 3 never: incomplete on the server.
+      ...post(500_000, 'Middle.Hole.2020.part1.rar', 3).slice(0, 2),
+    ], 600_000)
+    // Chunks without its part 3: the hole file is given up (idle) long before the end.
+    for (let at = 650_000; at < 950_000; at += 50_000) indexer.add([], at)
+    // Parts 1–2 near the end, still open when the range ends: part 3 is in the next range.
+    indexer.add(post(999_990, 'End.Cut.2020.part1.rar', 3).slice(0, 2), 1_000_001)
     indexer.finish()
     const batch = indexer.take()
-    assert.deepEqual(batch.fragments.map((f) => [f.name, f.segments.map((s) => [s[0], s[3]])]), [['Edge.File.2020.part1.rar', [[1, 5], [2, 6]]]])
-    assert.deepEqual(batch.counts.map((c) => [c.rule, c.articles]), [['incomplete', 2]])
+    assert.deepEqual(batch.fragments.map((f) => [f.name, f.segments.map((s) => s[0])]).sort(), [['End.Cut.2020.part1.rar', [1, 2]], ['Start.Cut.2020.part1.rar', [2, 3]]])
+    assert.deepEqual(batch.counts.map((c) => [c.rule, c.articles, c.files]), [['incomplete', 2, 1]])
     assert.lengthOf(batch.releases, 0)
   })
 })