Seed batches: insert files and binaries in chunks of 2,000 rows

A batch of a dense range (over ~5,400 files) exceeded Postgres' 65,535
bind parameters per statement, so its post failed with a 500 until the
range was given up.

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

tests/functional/seed.spec.ts

@@ -46,6 +46,20 @@ test.group('SeedService', (group) => {
     assert.include(again, { files: 0, existing: 2 })
   })
 
+  test('stores batches of more files than one INSERT can take', async ({ assert }) => {
+    // 12 columns per row: over 5,461 rows exceed Postgres' 65,535 bind parameters.
+    const aggregator = new FileAggregator<IngestSegment>()
+    const segments = Array.from({ length: 6000 }, (_, i) =>
+      segmentFromHeader(header(`Dense.Upload - [${i + 1}/6000] - "dense.${i + 1}.dat" yEnc (1/1)`, i + 1), 'alt.binaries.test', i + 1)!
+    )
+    const files = aggregator.add(segments).map(toSeedFile)
+    assert.lengthOf(files, 6000)
+    const result = await SeedService.store(files)
+    assert.include(result, { files: 6000 })
+    const [{ count }] = await db.from('binaries').whereLike('name', 'dense.%').whereNotNull('file_id').count('* as count')
+    assert.equal(Number(count), 6000)
+  }).timeout(60_000)
+
   test('fragments are kept near the range edges only', async ({ assert }) => {
     const subject = (name: string) => `Seed.Frag - "${name}" yEnc (1/3)`
     const edge = segmentFromHeader(header(subject('edge.bin'), 1), 'alt.binaries.test', 1_000_100)!