Derive the notation names from one table and refuse an smsIdFormat that is not the pair

test/session-extras.test.ts

@@ -872,6 +872,8 @@ describe('message id notation', () => {
 
 		assert.ok(checked.err instanceof Error);
 		assert.match(checked.err.message, /smsIdFormat\.receipt/);
+		// The shape todo.md sketched, which a caller without types would otherwise pass unnoticed.
+		assert.ok(checkSessionOptions({ smsIdFormat: 'hex' }).err instanceof Error);
 		assert.equal(checkSessionOptions({ smsIdFormat: { submitResp: 'hex' } }).err, undefined);
 	});
 });