refactor: ui.js, chat.js, history.js in 13 modulare Dateien aufteilen

Die monolithische ui.js (1534 Zeilen) zusammen mit chat.js (612) und
history.js (626) in fokussierte Module aufgeteilt:

Neue Dateien aus ui.js:
- ui-helpers.js (126) - DOM-Utilities, $, esc, truncate, scrollDown, Toast
- markdown.js (143) - renderMarkdown, wrapKreaGalleries, LaTeX/Code-Schutz
- cards.js (90) - buildSessionCard, buildAgentCard
- msg-actions.js (208) - Delete, Mark, Share, Reply-Button, Timestamp
- tool-ui.js (332) - Tool-Boxes, Diffs, Todo-Liste, Visibility
- modals.js (190) - System-Prompt, Command-Output, Krea-Image Modals
- stream-ui.js (124) - Stream-Bubble, Review-Streaming
- bubbles.js (312) - User/Assistant/Error/Warning/Choice/Review Bubbles

Neue Dateien aus chat.js:
- reply.js (54) - Reply/Quote-Handling mit pendingReply State
- files.js (110) - File-Upload, Workspace-Refs mit pendingFiles/Refs State

Neue Datei aus history.js:
- archive.js (173) - Archiv-Loading mit loadedArchiveCount State

Verbleibend:
- chat.js (448) - Stream-Events, sendMessage, handleChoiceClick, Plan-Mode
- history.js (464) - History laden, Polling, Message-Rendering

Kein Code verändert, nur verschoben. Alle 94 Funktionen verifiziert.
Globale Variablen in die Module verschoben, wo sie primär genutzt werden.

wwwroot/js/ui-helpers.js

@@ -0,0 +1,126 @@
+// ── DOM Helpers ──
+
+const $ = (sel) => document.querySelector(sel);
+const chatEl = () => $('#chat');
+const metaEl = () => $('#meta');
+
+function esc(s) {
+  const d = document.createElement('div');
+  d.textContent = s;
+  return d.innerHTML;
+}
+
+function truncate(s, max) {
+  return s && s.length > max ? s.substring(0, max) + '...' : (s || '');
+}
+
+function scrollDown() {
+  const chat = chatEl();
+  if (!chat) return;
+  chat.scrollTop = chat.scrollHeight;
+  // Nach Font-Swap kann sich die Höhe ändern → nochmal scrollen
+  document.fonts.ready.then(() => {
+    chat.scrollTop = chat.scrollHeight;
+  });
+}
+
+function prettyModelName(model) {
+  if (!model) return '?';
+  model = model.split('claude-').join('');
+  if (model == 'sonnet') return 'Sonnet';
+  if (model == 'sonnet-4-5') return 'Sonnet 4.5';
+  if (model == 'sonnet-4-6') return 'Sonnet 4.6';
+  if (model == 'opus') return 'Opus';
+  if (model == 'opus-4-5') return 'Opus 4.5';
+  if (model == 'opus-4-6') return 'Opus 4.6';
+  if (model == 'haiku') return 'Haiku';
+  if (model == 'haiku-4-5') return 'Haiku 4.5';
+  return 'Unbekannt (' + model + ')';
+}
+
+// ── Toast Notifications ──
+
+function showToast(message, type) {
+  type = type || 'info';
+  var container = document.getElementById('toastContainer');
+  if (!container) {
+    container = document.createElement('div');
+    container.id = 'toastContainer';
+    document.body.appendChild(container);
+  }
+  var toast = document.createElement('div');
+  toast.className = 'toast toast-' + type;
+  var icon = type === 'success' ? 'fa-check-circle' : type === 'error' ? 'fa-times-circle' : 'fa-info-circle';
+  toast.innerHTML = '<i class="fa ' + icon + '"></i> ' + (message || '');
+  container.appendChild(toast);
+  // Einblenden
+  requestAnimationFrame(function() { toast.classList.add('toast-visible'); });
+  // Automatisch ausblenden
+  var timeout = setTimeout(function() { removeToast(toast); }, 4000);
+  toast.addEventListener('click', function() {
+    clearTimeout(timeout);
+    removeToast(toast);
+  });
+}
+
+function removeToast(toast) {
+  toast.classList.remove('toast-visible');
+  toast.addEventListener('transitionend', function() { toast.remove(); });
+}
+
+// ── Meta Bar ──
+
+function setMeta(text) {
+  metaEl().textContent = text;
+}
+
+function setMetaHtml(html) {
+  metaEl().innerHTML = html;
+}
+
+// ── Older Messages Button ──
+
+function showOlderMessagesButton(remainingCount) {
+  removeOlderMessagesButton();
+  const btn = document.createElement('button');
+  btn.className = 'archive-load-btn older-messages-btn';
+  btn.innerHTML = '<i class="fa fa-arrow-up"></i> ' + remainingCount + ' ältere Nachrichten laden';
+  btn.addEventListener('click', () => loadOlderMessages());
+  chatEl().prepend(btn);
+}
+
+function removeOlderMessagesButton() {
+  const btn = chatEl().querySelector('.older-messages-btn');
+  if (btn) btn.remove();
+}
+
+// ── Archive Button ──
+
+function showArchiveLoadButton() {
+  const existing = chatEl().querySelector('.archive-load-btn:not(.older-messages-btn)');
+  if (existing) existing.remove();
+
+  const btn = document.createElement('button');
+  btn.className = 'archive-load-btn';
+  btn.innerHTML = '<i class="fa fa-archive"></i> Archivierte Nachrichten laden';
+  btn.addEventListener('click', loadLatestArchive);
+
+  // Immer ganz oben im Chat (aber nach dem older-messages-btn falls vorhanden)
+  const olderBtn = chatEl().querySelector('.older-messages-btn');
+  if (olderBtn) {
+    olderBtn.after(btn);
+  } else {
+    chatEl().prepend(btn);
+  }
+}
+
+function removeArchiveLoadButton() {
+  const btns = chatEl().querySelectorAll('.archive-load-btn:not(.older-messages-btn)');
+  btns.forEach(b => b.remove());
+}
+
+// ── Streamed Elements ──
+
+function removeStreamedElements() {
+  chatEl().querySelectorAll('.streamed').forEach(el => el.remove());
+}