Judge: count a chunk's file hashes once, from a covering index

The incremental judge counted each changed release's files twice, each
index entry a heap fetch: 24-32 s a chunk. file_hashes by (hash16k,
size, release_id) replaces (hash16k); the other releases of a file are
judged only when the chunk brings it to 20.

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

tests/functional/release_judge.spec.ts

@@ -171,6 +171,12 @@ test.group('ReleaseJudge', (group) => {
     const rules = new Set()
     for (const id of [...holders, twentieth]) rules.add(await verdict(id))
     assert.deepEqual([...rules], ['repeated'])
+    // A 21st: the file was in 20 releases without it, so only it is judged.
+    const twentyFirst = await release('holder20')
+    await db.table('file_hashes').insert({ candidate_id: 30020, release_id: twentyFirst, hash16k: hash, size: 5000 })
+    round = await judge.changed()
+    assert.equal(round.releases, 1)
+    assert.equal(await verdict(twentyFirst), 'repeated')
 
     // A verdict nothing noted stays until the full round; it's due a day after the last one.
     const stale = await release('Fine.Release')