An "ancient" range a group: articles 1 … low watermark − 1, never filled

Every group is tiled from article 1 now: one range with status 'ancient'
covers what had expired on the server before the group was planned.
Nothing selects it (leases, prefetcher, corpus fill, tail merger all take
'planned'), the status panel reports it apart, the search's history stats
leave it out. Migration 6700 adds it for the groups planned before;
Planner.historyRows (now a pure function, unit-tested) for new groups.
The status bands are ordered by an explicit key: the ancient row at
priority 0 tied "history 0-999" with "window 0".

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

tests/functional/status.spec.ts

@@ -94,6 +94,15 @@ test.group('Status', (group) => {
     ])
     await writeFile(join(dir, `${g.id}.gz`), Buffer.alloc(2_000_000))
     await writeFile(join(dir, `${g.id}-tail.gz`), Buffer.alloc(1000))
+    // A group planned from its low watermark 1000: its ancient range counts in no band and is never leased.
+    const [old] = await db
+      .table('groups')
+      .insert({ name: 'alt.binaries.ancient', priority: 2 })
+      .returning('id')
+    await db.table('ranges').multiInsert([
+      { group_id: old.id, start_id: 1, end_id: 999, next_id: 1, priority: 0, status: 'ancient' },
+      { group_id: old.id, start_id: 1000, end_id: 1099, next_id: 1000, priority: 0 },
+    ])
 
     const s = await StatusService.collect()
     assert.deepEqual(
@@ -111,10 +120,11 @@ test.group('Status', (group) => {
         ['raised', 1, 100, 0, 0, 0, 0],
         ['window 0', 0, 0, 1, 1, 100, 0],
         ['window 2', 1, 100, 0, 0, 0, 0],
-        ['history 0-999', 1, 100, 0, 0, 0, 0],
+        ['history 0-999', 2, 200, 0, 0, 0, 0],
         ['history 4000+', 0, 0, 0, 0, 0, 1],
       ]
     )
+    assert.deepEqual(s.ancient, { groups: 1, articles: 999 })
     assert.deepEqual(s.lastHour, {
       indexedArticles: 100,
       doneRanges: 1,
@@ -153,5 +163,6 @@ test.group('Status', (group) => {
     assert.include(text, 'window 0')
     assert.include(text, 'alt.binaries.status  history  status-node  301-400  351')
     assert.include(text, 'Snapshots: 2 files')
+    assert.include(text, 'Ancient: 999 articles below the low watermark of 1 groups')
   })
 })