fix(types): remove non-null assertions in remaining 12 files

Files fixed:
- messages-media.ts: stream/buffer guards, file path validation
- decode-wa-message.ts: message field guards, optional chaining
- version-cache.ts: narrowing after null checks
- jid-utils.ts: split result guards, user fallbacks
- communities.ts: attrs fallbacks with ?? operator
- sticker-pack.ts: response guards
- business.ts: attrs guards
- socket.ts: onClose guard, pairingCode guard, creds.me guard
- event-buffer.ts: null guards
- signal.ts: null guards
- encode.ts (WAM): id null check with continue
- upstream history.ts: conversations/pushnames null guards

All 26 files across the project are now corrected.
Total: ~248 non-null assertions replaced with proper null guards.

https://claude.ai/code/session_01E2cfX1N3sJgCJBTvzGazSG

upstream-baileys-pr/src/Utils/history.ts

@@ -194,9 +194,13 @@ export const processHistoryMessage = (item: proto.IHistorySync) => {
 		case proto.HistorySync.HistorySyncType.RECENT:
 		case proto.HistorySync.HistorySyncType.FULL:
 		case proto.HistorySync.HistorySyncType.ON_DEMAND:
-			for (const chat of item.conversations! as Chat[]) {
+			for (const chat of (item.conversations ?? []) as Chat[]) {
+				if (!chat.id) {
+					continue
+				}
+
 				contacts.push({
-					id: chat.id!,
+					id: chat.id,
 					name: chat.name || undefined,
 					lid: chat.lidJid || undefined,
 					phoneNumber: chat.pnJid || undefined
@@ -204,7 +208,7 @@ export const processHistoryMessage = (item: proto.IHistorySync) => {
 
 				// Source 2: Extract from conversation metadata
 				addLidPnMapping(
-					extractLidPnFromConversation(chat.id!, chat.lidJid, chat.pnJid)
+					extractLidPnFromConversation(chat.id, chat.lidJid, chat.pnJid)
 				)
 
 				const msgs = chat.messages || []
@@ -242,7 +246,7 @@ export const processHistoryMessage = (item: proto.IHistorySync) => {
 						message.messageStubParameters?.[0]
 					) {
 						contacts.push({
-							id: message.key.participant || message.key.remoteJid!,
+							id: message.key.participant || message.key.remoteJid || '',
 							verifiedName: message.messageStubParameters?.[0]
 						})
 					}
@@ -253,8 +257,12 @@ export const processHistoryMessage = (item: proto.IHistorySync) => {
 
 			break
 		case proto.HistorySync.HistorySyncType.PUSH_NAME:
-			for (const c of item.pushnames!) {
-				contacts.push({ id: c.id!, notify: c.pushname! })
+			for (const c of item.pushnames ?? []) {
+				if (!c.id) {
+					continue
+				}
+
+				contacts.push({ id: c.id, notify: c.pushname ?? '' })
 			}
 
 			break