feat: Auto-Context im Frontend anzeigen und in DB persistieren

- recalled_context-Header verstärkt (klare Nutzungs-Anweisung statt passivem Hinweis)
- SSE-Event 'auto_context' ans Frontend senden für Live-Anzeige
- Auto-Context als Message (type=auto_context) in DB speichern
- Aufklappbare Auto-Context-Box im Chat-Stream und History-Rendering

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

wwwroot/js/stream-ui.js

@@ -103,6 +103,28 @@ function endThinkingBubble() {
   _thinkingText = '';
 }
 
+// ── Auto-Context Bubble ──
+
+function addAutoContextBubble(contextText) {
+  if (!contextText) return;
+  var box = document.createElement('div');
+  box.className = 'tool-box auto-context-box streamed';
+  var header = document.createElement('div');
+  header.className = 'tool-box-header clickable';
+  header.innerHTML = '<span class="tool-name">Auto-Context</span>';
+  var content = document.createElement('div');
+  content.className = 'auto-context-content markdown';
+  content.hidden = true;
+  // recalled_context aus XML-Tags extrahieren
+  var inner = contextText.replace(/<\/?recalled_context>/g, '').trim();
+  content.innerHTML = renderMarkdown(inner);
+  header.addEventListener('click', function() { content.hidden = !content.hidden; });
+  box.appendChild(header);
+  box.appendChild(content);
+  chatEl().appendChild(box);
+  scrollDown();
+}
+
 // ── Review Bubbles (Streaming) ──
 
 let _reviewBubble = null;