angularjs sanitize not work properly with ng-model - angularjs

Question

I use AntiXss Encoder on serverside for XSS atacks so all response includes html unescape characters like "&lt:script&gt:alert(1);&lt:/script&gt:" (replaced ';' as ':')
on binding i use sanitize with ng-bind-html there is no problem wih that.
There is an other control input for update mode. When user needs to update text they click update icon then i show textarea and hide binded tag with ng-if. textarea has ng-model attr. i cant escape html characters on textarea like ng-bind-html here is the snippet pls help im getting creazy..
in fiddle; edit mode textarea must display "<script>alert(1);</script>" with no alert action and data will be sent to the server must display same too...
here is the fiddle
var app = angular.module('myApp',['ngSanitize']);
app.controller('MyCtrl', function($scope, $sce, $sanitize) {
$scope.post1 = "<script>alert(1);</script>";
//$scope.post2 = $sce.parseAsHtml("<h1>alert(1)</h1>");
$scope.logs = ["log created"];
$scope.log = function(val){
$scope.logs.push(val);
}
});
.label {
text-decoration:underline;
color:red;
}
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular-sanitize.min.js"></script>
<div ng-app="myApp">
<div ng-controller="MyCtrl">
<div class="label">Edit mode :</div>
<textarea ng-model="post1" style="width:100%;" rows="5"></textarea><br />
<div class="label">Binding mode :</div>
<div ng-bind-html="post1"></div><br />
<div class="label">Data will be send to the server :</div>
<div>{{post1}}</div><br />
<div class="label">Logs (if needed) :</div>
<div ng-repeat="d in logs">
<p>{{($index+1) + ". " + d}}</p>
</div>
</div>
</div>