Simplify steering input placeholder text

Shorten the streaming-mode input placeholder from
"💬 Einwurf an die laufende Arbeit… (Enter)" to a terse "Einwurf...".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

wwwroot/js/chat.js

@@ -297,7 +297,7 @@ async function _runStream(fetchPromise) {
   const _steerInputEl = $('#input');
   const _prevPlaceholder = _steerInputEl ? _steerInputEl.placeholder : '';
   if (_steerInputEl) {
-    _steerInputEl.placeholder = '💬 Einwurf an die laufende Arbeit… (Enter)';
+    _steerInputEl.placeholder = 'Einwurf...';
     _steerInputEl.classList.add('steer-mode');
   }