Chat tabs, chat mode, own modes, compaction notice, CLI binaries again

- Terminals and file managers as tabs of a chat; chat terminals keep running on
  the server (no idle timeout) and re-attach from any device
- "Just chat" in New session and a built-in chat mode with a lean prompt and only
  web tools; custom modes with kind (coding/conversation), read-only and tool picker
- Mode selector as a dropdown
- The chat shows running compactions (automatic: tokens and share of the limit)
  and labels summaries
- Docker image builds and serves the terminal client binaries again
- Fix: atomic session updates; background title/usage writes no longer undo each
  other (auto compaction triggered one turn late)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/whatsnew.ts

@@ -4,8 +4,22 @@
  */
 export const WHATS_NEW: Record<string, { en: string[]; de: string[] }> = {
   unreleased: {
-    en: ["File manager: “Open chat here” in a folder's menu"],
-    de: ["Dateimanager: „Chat hier öffnen“ im Ordner-Menü"],
+    en: [
+      "Terminals and file managers as tabs in a chat – terminals keep running, also for another device",
+      "New session → “Just chat” for plain conversation",
+      "Own modes: Settings → Agents & commands → New mode",
+      "The chat shows when the conversation is compacted (automatically or on request)",
+      "File manager: “Open chat here” in a folder's menu",
+      "Terminal client downloadable from the server again",
+    ],
+    de: [
+      "Terminals und Dateimanager als Tabs im Chat – Terminals laufen weiter, auch für ein anderes Gerät",
+      "Neue Sitzung → „Einfach chatten“ für reine Unterhaltung",
+      "Eigene Modi: Einstellungen → Agents & Befehle → Neuer Modus",
+      "Der Chat zeigt an, wenn die Unterhaltung komprimiert wird (automatisch oder auf Wunsch)",
+      "Dateimanager: „Chat hier öffnen“ im Ordner-Menü",
+      "Terminal-Client wieder direkt vom Server herunterladbar",
+    ],
   },
   "202611-00002": {
     en: [