Rebuild: phase 1 modules from the current app, ordered by pipeline stage

lib/nntp (XOVER client, Xref, GROUP), lib/headers (subjects, file keys,
segments from overview lines; the yEnc path stays behind for phase 2),
lib/release (identity, random names, now in lib), lib/files (aggregator,
volume names), lib/rules (posting tools, owner by priority, release
verdicts), lib/chunks (release chunk codec). Their unit tests came along;
new ones for codec, rules and volumes.

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

tests/unit/files/aggregator.spec.ts

@@ -0,0 +1,39 @@
+import { test } from '@japa/runner'
+import { FileAggregator, type AggregatableSegment } from '#lib/files/index'
+
+const seg = (fileKey: string, number: number, totalParts: number, messageId = `${fileKey}-${number}@test`): AggregatableSegment => ({
+  fileKey,
+  number,
+  totalParts,
+  messageId,
+  bytes: 100,
+})
+
+test.group('aggregate / FileAggregator', () => {
+  test('completes a file once every part arrived, across batches and out of order', ({ assert }) => {
+    const aggregator = new FileAggregator()
+    assert.deepEqual(aggregator.add([seg('a', 2, 3), seg('b', 1, 1)]).map((f) => f.fileKey), ['b'])
+    assert.equal(aggregator.openFiles, 1)
+    const [done] = aggregator.add([seg('a', 3, 3), seg('a', 1, 3)])
+    assert.equal(done.fileKey, 'a')
+    assert.deepEqual(done.segments.map((s) => s.number), [1, 2, 3])
+    assert.equal(aggregator.openFiles, 0)
+  })
+
+  test('keeps the first article of a part number (a repost) and drops impossible numbers', ({ assert }) => {
+    const aggregator = new FileAggregator()
+    const [done] = aggregator.add([seg('a', 1, 2, 'first@test'), seg('a', 1, 2, 'repost@test'), seg('a', 5, 2), seg('a', 2, 2)])
+    assert.deepEqual(done.segments.map((s) => s.messageId), ['first@test', 'a-2@test'])
+    assert.deepEqual(aggregator.evict().map((s) => s.number), [5])
+  })
+
+  test('gives up idle files as fragments, all of them at the end', ({ assert }) => {
+    const aggregator = new FileAggregator()
+    aggregator.add([seg('old', 1, 3)])
+    aggregator.add([seg('new', 1, 3)])
+    aggregator.add([seg('new', 2, 3)])
+    assert.deepEqual(aggregator.evict(2).map((s) => s.fileKey), ['old'])
+    assert.deepEqual(aggregator.evict(0).map((s) => s.number), [1, 2])
+    assert.equal(aggregator.openFiles, 0)
+  })
+})