perf: optimize history sync memory and CPU usage (#385)

* perf: optimize history sync memory and CPU usage

Aligns with Baileys upstream PR #2333 . Surgical port of
4 micro-optimizations + 2 test files. No collision with InfiniteAPI's
LID/PN, carousel, buttons, Bad MAC or app state sync resilience code.

Changes:

1. WAProto longToString/longToNumber: use native BigInt instead of
   Long library division loops. ~4.6x faster per call (237ns -> 52ns).
   BigInt.toString() delegates to V8 native C++. Same change applied
   to fix-imports.js (template) and index.js (generated artifact) so
   future regenerations stay in sync.

2. downloadHistory: stream-pipe createInflate instead of buffering
   the full compressed payload then inflating. Cuts RSS peak ~50%
   on 50MB history payloads.

3. processHistoryMessage: drop the { ...chat } shallow copy before
   pushing to chats[]. The decoded protobuf object is not referenced
   after the push.

4. downloadEncryptedContent transform: skip Buffer.concat when
   remainingBytes is empty (the common case — chunks usually arrive
   AES-aligned). ~19x faster per chunk (78ms -> 4ms over 25k chunks).

Tests:
- bigint-validation.test.ts (NEW): 32 parameterized cases covering
  zero, MAX_SAFE_INTEGER boundary, max int64/uint64, negative values,
  tricky bit patterns and powers of 2; plus 200-iter fuzz comparing
  old Long vs new BigInt implementations for equivalence.
- proto-tojson-long.test.ts: kept the existing fork-only test for
  string-in-Long-field graceful handling, appended 4 upstream tests
  covering Long->string fast path, large unsigned > MAX_SAFE_INTEGER,
  zero/small values and encode/decode roundtrip.

src/Utils/history.ts

@@ -1,5 +1,6 @@
+import { pipeline } from 'stream/promises'
 import { promisify } from 'util'
-import { inflate } from 'zlib'
+import { createInflate, inflate } from 'zlib'
 import { proto } from '../../WAProto/index.js'
 import type { Chat, Contact, LIDMapping, WAMessage } from '../Types'
 import { WAMessageStubType } from '../Types'
@@ -29,16 +30,15 @@ const inflatePromise = promisify(inflate)
  */
 export const downloadHistory = async (msg: proto.Message.IHistorySyncNotification, options: RequestInit) => {
 	const stream = await downloadContentFromMessage(msg, 'md-msg-hist', { options })
-	const bufferArray: Buffer[] = []
-	for await (const chunk of stream) {
-		bufferArray.push(chunk)
-	}
-
-	let buffer: Buffer = Buffer.concat(bufferArray)
-
-	// decompress buffer
-	buffer = await inflatePromise(buffer)
+	// Pipe decrypted stream directly through zlib inflate.
+	// Avoids allocating an intermediate buffer for the compressed payload —
+	// memory peaks during 50MB history syncs drop ~50% (PR upstream #2333).
+	const inflater = createInflate()
+	const chunks: Buffer[] = []
+	inflater.on('data', (chunk: Buffer) => chunks.push(chunk))
+	await pipeline(stream, inflater)
 
+	const buffer = Buffer.concat(chunks)
 	const syncData = proto.HistorySync.decode(buffer)
 	return syncData
 }
@@ -361,7 +361,7 @@ export const processHistoryMessage = (item: proto.IHistorySync, logger?: ILogger
 					}
 				}
 
-				chats.push({ ...chat })
+				chats.push(chat)
 			}
 
 			break

src/Utils/messages-media.ts

@@ -618,7 +618,7 @@ export const downloadEncryptedContent = async (
 
 	const output = new Transform({
 		transform(chunk, _, callback) {
-			let data = Buffer.concat([remainingBytes, chunk])
+			let data = remainingBytes.length ? Buffer.concat([remainingBytes, chunk]) : chunk
 
 			const decryptLength = toSmallestChunkSize(data.length)
 			remainingBytes = data.slice(decryptLength)