style: add eslint-disable comments for intentional == null checks

Added // eslint-disable-next-line eqeqeq comments for intentional null/undefined checks:
- sender-key-message.ts: checking for null OR undefined parameters
- WAM/encode.ts: checking for null OR undefined id
- baileys-event-stream.test.ts: renamed unused event parameter to _event

These changes are COSMETIC ONLY - no logic changed:
- Build still passes ✅
- All tests still work ✅
- API behavior unchanged ✅

The == null pattern is intentionally used to check for BOTH null AND undefined,
which is the correct behavior for these optional parameters.

https://claude.ai/code/session_015R3U3kiprQiNTTNNt31Sg6

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

@@ -42,6 +42,7 @@ export class SenderKeyMessage extends CiphertextMessage {
 					: senderKeyMessage.ciphertext
 			this.signature = signature
 		} else {
+			// eslint-disable-next-line eqeqeq
 			if (ciphertext == null || keyId == null || iteration == null || signatureKey == null) {
 				throw new Error('Missing required parameters for SenderKeyMessage construction')
 			}