fix(types): resolve all TypeScript compilation errors from non-null assertion removal

Fixes:
- chats.ts: revert encodeResult/initial to ! (guaranteed by callback assignment)
- groups.ts: fix operator precedence with ?? (wrap +attrs in parens), fix groupId type
- messages-recv.ts: extract messageKey.id to local const with fallback
- socket.ts: revert onClose! (guaranteed by synchronous callback assignment)
- event-buffer.ts: add 'notify' fallback for MessageUpsertType
- messages.ts: add filePath const after null guard, fix contextInfo type assertion
- noise-handler.ts: restore array index ! (guaranteed by length check)

Build now compiles with zero new errors.

https://claude.ai/code/session_01E2cfX1N3sJgCJBTvzGazSG

src/Socket/groups.ts

@@ -316,7 +316,7 @@ export const extractGroupMetadata = (result: BinaryNode) => {
 		descId = descChild.attrs.id
 	}
 
-	const groupId = (group.attrs.id ?? '').includes('@') ? group.attrs.id : jidEncode(group.attrs.id ?? '', 'g.us')
+	const groupId = (group.attrs.id ?? '').includes('@') ? (group.attrs.id ?? '') : jidEncode(group.attrs.id ?? '', 'g.us')
 	const eph = getBinaryNodeChild(group, 'ephemeral')?.attrs.expiration
 	const memberAddMode = getBinaryNodeChildString(group, 'member_add_mode') === 'all_member_add'
 	const metadata: GroupMetadata = {
@@ -326,9 +326,9 @@ export const extractGroupMetadata = (result: BinaryNode) => {
 		subject: group.attrs.subject ?? '',
 		subjectOwner: group.attrs.s_o,
 		subjectOwnerPn: group.attrs.s_o_pn,
-		subjectTime: +group.attrs.s_t ?? '0',
+		subjectTime: +(group.attrs.s_t ?? '0'),
 		size: group.attrs.size ? +group.attrs.size : getBinaryNodeChildren(group, 'participant').length,
-		creation: +group.attrs.creation ?? '0',
+		creation: +(group.attrs.creation ?? '0'),
 		owner: group.attrs.creator ? jidNormalizedUser(group.attrs.creator) : undefined,
 		ownerPn: group.attrs.creator_pn ? jidNormalizedUser(group.attrs.creator_pn) : undefined,
 		owner_country_code: group.attrs.creator_country_code,