Rebuild: chunks the server's compression cuts short are fetched plain

Eweka sends some ranges' compressed XOVER truncated, the same bytes
every time, while the plain reply is whole (a.b.models 3317215-3367214:
1,675,600 bytes that don't inflate, twice; 50,000 lines plain;
tools/false_end.ts). Not a false end of reply. The worker's corrupt
report removed the chunk and the range was fetched again, with the same
bytes: one range was reported 540 times. (Before this morning's change
the inflate check waited for more data until the 10-minute timeout,
like voyager 1's 'chunk never answered' ranges.)

A reported chunk's start goes into ranges.plain_chunks; the prefetcher
fetches those over one connection without XFEATURE COMPRESS GZIP
(NntpPool.usePlain, opened on demand) and deflates them here. A plain
chunk reported again sets the range aside (status failed, error). The
capture (edge:bench --capture) fetches such a chunk plain too.

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

tests/functional/node_api.spec.ts

@@ -98,10 +98,19 @@ test.group('Node API', (group) => {
       await Promise.all(Spool.chunksOf({ start: 1, end: 300 }).map((span) => Spool.has(rangeId, span))),
       [true, false, true]
     )
-    const range = await db.from('ranges').where('id', rangeId).first()
+    let range = await db.from('ranges').where('id', rangeId).first()
     assert.equal(range.status, 'planned')
     assert.isNull(range.node_id)
+    // Fetched plain next time (the server's compressed reply was cut short).
+    assert.deepEqual(range.plain_chunks.map(Number), [101])
     // No longer this node's: a second report is refused.
     ;(await client.post(`/api/v1/node/ranges/${rangeId}/corrupt`).bearerToken(token).json({ from: 101 })).assertStatus(409)
+    // Leased again and the plain chunk still doesn't inflate: the range is set aside, not leased in a loop.
+    await Spool.write(rangeId, { from: 101, to: 200 }, chunk(111))
+    ;(await client.post('/api/v1/node/lease').bearerToken(token)).assertStatus(200)
+    ;(await client.post(`/api/v1/node/ranges/${rangeId}/corrupt`).bearerToken(token).json({ from: 101 })).assertStatus(200)
+    range = await db.from('ranges').where('id', rangeId).first()
+    assert.equal(range.status, 'failed')
+    assert.include(range.error, 'also fetched plain')
   })
 })