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>

lib/headers/segment.ts

@@ -0,0 +1,72 @@
+import { parseXrefGroups } from '../nntp/xref.js'
+import { fileKey } from './file_key.js'
+import { parseSubject } from './subject.js'
+import { releaseIdentity, type ReleaseIdentity } from '../release/index.js'
+
+/** One segment, with the identity of the file it belongs to already resolved. */
+export interface IngestSegment {
+  fileKey: string
+  poster: string
+  /** Subject without segment counter. */
+  subject: string
+  name: string
+  totalParts: number
+  number: number
+  /** Without angle brackets. */
+  messageId: string
+  bytes: number
+  articleNumber?: bigint | number
+  postedAt?: Date
+  groups: string[]
+  /**
+   * The identity comes from the yEnc name only (obfuscated posts). Such names
+   * can be shared by several equal-sized files of one post, so a second
+   * article for the same part number marks the binary as conflicted.
+   */
+  weakIdentity?: boolean
+  /** Release (download) this file belongs to, when it can be determined. */
+  release?: ReleaseIdentity | null
+  /** Exact file size from =ybegin (body-derived segments only). */
+  size?: number
+  /** yEnc CRCs (body-derived segments only), to verify split volumes. */
+  pcrc32?: string
+  partSize?: number
+  fileCrc32?: string
+  /** Part 1 only: MD5 of the first 16 KiB of the file, as par2 records it. */
+  md5_16k?: string
+}
+
+/** An XOVER overview entry as returned by nntp-js. */
+export type OverviewHeader = Record<string, string>
+
+function common(header: OverviewHeader, groupName: string, articleNumber?: bigint | number) {
+  const xrefGroups = parseXrefGroups(header.xref)
+  return {
+    poster: header.from ?? '',
+    messageId: (header['message-id'] ?? '').replace(/^<|>$/g, ''),
+    bytes: Number.parseInt(header[':bytes'] ?? '0', 10) || 0,
+    articleNumber,
+    postedAt: header.date ? new Date(header.date) : undefined,
+    groups: xrefGroups.length > 0 ? xrefGroups : [groupName],
+  }
+}
+
+/** Builds a segment from the subject line; null when the subject is obfuscated. */
+export function segmentFromHeader(
+  header: OverviewHeader,
+  groupName: string,
+  articleNumber?: bigint | number
+): IngestSegment | null {
+  const parsed = header.subject ? parseSubject(header.subject) : null
+  if (!parsed || !header['message-id']) return null
+  const base = common(header, groupName, articleNumber)
+  return {
+    ...base,
+    fileKey: fileKey(base.poster, parsed.base, parsed.totalSegments),
+    subject: parsed.base,
+    name: parsed.name,
+    totalParts: parsed.totalSegments,
+    number: parsed.segment,
+    release: releaseIdentity({ poster: base.poster, subject: parsed.base, name: parsed.name, weak: false }),
+  }
+}