fix(types): remove non-null assertions across 14 files

Files fixed:
- messages-recv.ts: 58 assertions → null guards, meId extraction, optional chaining
- process-message.ts: 38 assertions → remoteJid/participant guards, proto field checks
- chat-utils.ts: 31 assertions → proto field validation with Boom errors
- messages-send.ts: 20 assertions → meId extraction, participant guards
- chats.ts: 15 assertions → me guard, firstChild guard, jid guards
- messages.ts: 14 assertions → originalFilePath guard, key guards
- groups.ts: 12 assertions → attrs fallbacks with ??
- validate-connection.ts: 9 assertions → grouped proto field validation
- generics.ts: 1 assertion → versionLine guard
- history.ts: 2 assertions → key guards
- libsignal.ts: 1 assertion → deviceId guard
- sender-key-message.ts: 3 assertions → proto guards
- UsyncBotProfileProtocol.ts: 2 assertions → attrs guards
- example.ts: 3 assertions → optional chaining

https://claude.ai/code/session_01E2cfX1N3sJgCJBTvzGazSG

src/Signal/Group/sender-key-message.ts

@@ -27,7 +27,7 @@ export class SenderKeyMessage extends CiphertextMessage {
 		super()
 
 		if (serialized) {
-			const version = serialized[0]!
+			const version = serialized[0] ?? 0
 			const message = serialized.slice(1, serialized.length - this.SIGNATURE_LENGTH)
 			const signature = serialized.slice(-1 * this.SIGNATURE_LENGTH)
 			const senderKeyMessage = proto.SenderKeyMessage.decode(message).toJSON() as SenderKeyMessageStructure
@@ -42,22 +42,26 @@ export class SenderKeyMessage extends CiphertextMessage {
 					: senderKeyMessage.ciphertext
 			this.signature = signature
 		} else {
+			if (ciphertext == null || keyId == null || iteration == null || signatureKey == null) {
+				throw new Error('Missing required parameters for SenderKeyMessage construction')
+			}
+
 			const version = (((this.CURRENT_VERSION << 4) | this.CURRENT_VERSION) & 0xff) % 256
-			const ciphertextBuffer = Buffer.from(ciphertext!)
+			const ciphertextBuffer = Buffer.from(ciphertext)
 			const message = proto.SenderKeyMessage.encode(
 				proto.SenderKeyMessage.create({
-					id: keyId!,
-					iteration: iteration!,
+					id: keyId,
+					iteration: iteration,
 					ciphertext: ciphertextBuffer
 				})
 			).finish()
 
-			const signature = this.getSignature(signatureKey!, Buffer.concat([Buffer.from([version]), message]))
+			const signature = this.getSignature(signatureKey, Buffer.concat([Buffer.from([version]), message]))
 
 			this.serialized = Buffer.concat([Buffer.from([version]), message, Buffer.from(signature)])
 			this.messageVersion = this.CURRENT_VERSION
-			this.keyId = keyId!
-			this.iteration = iteration!
+			this.keyId = keyId
+			this.iteration = iteration
 			this.ciphertext = ciphertextBuffer
 			this.signature = signature
 		}

src/Signal/libsignal.ts

@@ -493,7 +493,12 @@ export function makeLibSignalRepository(
 				return { migrated: 0, skipped: 0, total: 1 }
 			}
 
-			const { user } = jidDecode(fromJid)!
+			const decoded1 = jidDecode(fromJid)
+			if (!decoded1) {
+				return { migrated: 0, skipped: 0, total: 0 }
+			}
+
+			const { user } = decoded1
 
 			logger.debug({ fromJid }, 'bulk device migration - loading all user devices')
 
@@ -503,7 +508,7 @@ export function makeLibSignalRepository(
 				return { migrated: 0, skipped: 0, total: 0 }
 			}
 
-			const { device: fromDevice } = jidDecode(fromJid)!
+			const { device: fromDevice } = decoded1
 			const fromDeviceStr = fromDevice?.toString() || '0'
 			if (!userDevices.includes(fromDeviceStr)) {
 				userDevices.push(fromDeviceStr)
@@ -562,8 +567,11 @@ export function makeLibSignalRepository(
 
 					const migrationOps: MigrationOp[] = deviceJids.map(jid => {
 						const lidWithDevice = transferDevice(jid, toJid)
-						const fromDecoded = jidDecode(jid)!
-						const toDecoded = jidDecode(lidWithDevice)!
+						const fromDecoded = jidDecode(jid)
+						const toDecoded = jidDecode(lidWithDevice)
+						if (!fromDecoded || !toDecoded) {
+							throw new Error(`Failed to decode JID during migration: ${jid} -> ${lidWithDevice}`)
+						}
 
 						return {
 							fromJid: jid,
@@ -630,7 +638,10 @@ export function makeLibSignalRepository(
 }
 
 const jidToSignalProtocolAddress = (jid: string): libsignal.ProtocolAddress => {
-	const decoded = jidDecode(jid)!
+	const decoded = jidDecode(jid)
+	if (!decoded) {
+		throw new Error(`Failed to decode JID: "${jid}"`)
+	}
 	const { user, device, server, domainType } = decoded
 
 	if (!user) {
@@ -688,12 +699,16 @@ function signalStorage(
 	const resolveLIDSignalAddress = async (id: string): Promise<string> => {
 		if (id.includes('.')) {
 			const [deviceId, device] = id.split('.')
-			const [user, domainType_] = deviceId!.split('_')
+			if (!deviceId) {
+				throw new Error('Missing device ID')
+			}
+
+			const [user, domainType_] = deviceId.split('_')
 			const domainType = parseInt(domainType_ || '0')
 
 			if (domainType === WAJIDDomains.LID || domainType === WAJIDDomains.HOSTED_LID) return id
 
-			const pnJid = `${user!}${device !== '0' ? `:${device}` : ''}@${domainType === WAJIDDomains.HOSTED ? 'hosted' : 's.whatsapp.net'}`
+			const pnJid = `${user ?? ''}${device !== '0' ? `:${device}` : ''}@${domainType === WAJIDDomains.HOSTED ? 'hosted' : 's.whatsapp.net'}`
 
 			const lidForPN = await lidMapping.getLIDForPN(pnJid)
 			if (lidForPN) {