feat(worker): fingerprint listing-less ZIP candidates via destination copy

Rebuild-created placeholder candidates have no PackageFile CRCs, so
name-side fingerprinting can't confirm them. When the stored candidate
fingerprint is incomplete, read the candidate's own copy from its
destination message and fingerprint against that instead of falling
straight to name+size confidence.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

worker/src/db/queries.ts

@@ -1012,12 +1012,25 @@ export async function createAutoGroup(input: {
 
 // ── Provenance backfill ──
 
+export interface PlaceholderCandidate {
+  id: string;
+  archiveType: string;
+  fileCount: number;
+  fileSize: bigint;
+  destMessageId: bigint | null;
+  destMessageIds: bigint[];
+  destChannel: { telegramId: bigint } | null;
+}
+
 export async function findPlaceholderCandidate(
   destChannelId: string,
   fileName: string,
   fileSize: bigint,
-): Promise<{ id: string; archiveType: string; fileCount: number } | null> {
-  return db.package.findFirst({
+): Promise<PlaceholderCandidate | null> {
+  // Package has no direct `destChannel` relation (only the scalar
+  // `destChannelId`), so resolve the destination TelegramChannel's
+  // telegramId with a follow-up lookup rather than a Prisma include.
+  const row = await db.package.findFirst({
     where: {
       fileName,
       fileSize,
@@ -1029,9 +1042,28 @@ export async function findPlaceholderCandidate(
         { sourceMessageId: 0n },
       ],
     },
-    select: { id: true, archiveType: true, fileCount: true },
+    select: {
+      id: true, archiveType: true, fileCount: true, fileSize: true,
+      destMessageId: true, destMessageIds: true, destChannelId: true,
+    },
     orderBy: { indexedAt: "asc" },
   });
+  if (!row) return null;
+  const destChannel = row.destChannelId
+    ? await db.telegramChannel.findUnique({
+        where: { id: row.destChannelId },
+        select: { telegramId: true },
+      })
+    : null;
+  return {
+    id: row.id,
+    archiveType: row.archiveType,
+    fileCount: row.fileCount,
+    fileSize: row.fileSize,
+    destMessageId: row.destMessageId,
+    destMessageIds: row.destMessageIds,
+    destChannel,
+  };
 }
 
 export async function getPackageFileCrcs(packageId: string): Promise<(string | null)[]> {

worker/src/provenance-backfill.ts

@@ -1,7 +1,8 @@
 import { childLogger } from "./util/logger.js";
 import { downloadFileRange } from "./tdlib/range-download.js";
+import { invokeWithTimeout } from "./tdlib/download.js";
 import { parseZipCentralDirectoryFromTail, MIN_ZIP_TAIL_BYTES } from "./archive/central-directory.js";
-import { fingerprintsMatch } from "./archive/fingerprint.js";
+import { fingerprintsMatch, crcFingerprint } from "./archive/fingerprint.js";
 import {
   findPlaceholderCandidate,
   getPackageFileCrcs,
@@ -49,6 +50,28 @@ async function readScannedZipListing(
   return null;
 }
 
+async function readZipListingFromDestination(
+  client: Client,
+  destChatTelegramId: bigint,
+  destMessageId: bigint,
+  fileSize: bigint,
+): Promise<FileEntry[] | null> {
+  try {
+    // Resolve the destination message's document file id.
+    const msg = (await invokeWithTimeout(client, {
+      _: "getMessage",
+      chat_id: Number(destChatTelegramId),
+      message_id: Number(destMessageId),
+    })) as { content?: { document?: { document?: { id: number } } } };
+    const fid = msg?.content?.document?.document?.id;
+    if (!fid) return null;
+    return await readScannedZipListing(client, String(fid), fileSize);
+  } catch (err) {
+    log.warn({ err, destMessageId: Number(destMessageId) }, "destination ZIP listing read failed");
+    return null;
+  }
+}
+
 export async function tryProvenanceBackfill(
   args: BackfillArgs,
 ): Promise<{ backfilled: boolean; confidence?: "fingerprint" | "name-size" }> {
@@ -62,9 +85,24 @@ export async function tryProvenanceBackfill(
     entries = await readScannedZipListing(args.client, args.scannedFileId, args.fileSize);
     if (entries) {
       const candidateCrcs = await getPackageFileCrcs(candidate.id);
-      const candidateEntries: FileEntry[] = candidateCrcs.map((crc) => ({
+      let candidateEntries: FileEntry[] = candidateCrcs.map((crc) => ({
         path: "", fileName: "", extension: null, compressedSize: 0n, uncompressedSize: 0n, crc32: crc,
       }));
+      const destMessageId =
+        candidate.destMessageIds.length > 0
+          ? candidate.destMessageIds[candidate.destMessageIds.length - 1]
+          : candidate.destMessageId;
+      if (!crcFingerprint(candidateEntries).complete && destMessageId && candidate.destChannel) {
+        const destEntries = await readZipListingFromDestination(
+          args.client,
+          candidate.destChannel.telegramId,
+          destMessageId,
+          candidate.fileSize,
+        );
+        if (destEntries) {
+          candidateEntries = destEntries;
+        }
+      }
       if (fingerprintsMatch(entries, candidateEntries)) {
         confidence = "fingerprint";
       } else {