feat(web): add WebSocket transport for message event streaming with SSE fallback (#764)

* feat: add websocket message stream transport

* fix: avoid false missing session directories in sidebar

* fix: re-probe project root session directories

* refactor: use button group for message stream transport

* fix: resolve chat input hook dependency warning

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/lib/api/types.ts

@@ -569,6 +569,7 @@ export interface SettingsPayload {
   showExpandedBashTools?: boolean;
   showExpandedEditTools?: boolean;
   chatRenderMode?: 'sorted' | 'live';
+  messageStreamTransport?: 'auto' | 'ws' | 'sse';
   activityRenderMode?: 'collapsed' | 'summary';
   mermaidRenderingMode?: 'svg' | 'ascii';
   fontSize?: number;

packages/ui/src/lib/desktop.ts

@@ -125,6 +125,7 @@ export type DesktopSettings = {
   timeFormatPreference?: 'auto' | '12h' | '24h';
   weekStartPreference?: 'auto' | 'sunday' | 'monday';
   chatRenderMode?: 'sorted' | 'live';
+  messageStreamTransport?: 'auto' | 'ws' | 'sse';
   activityRenderMode?: 'collapsed' | 'summary';
   mermaidRenderingMode?: 'svg' | 'ascii';
   userMessageRenderingMode?: 'markdown' | 'plain';

packages/ui/src/lib/persistence.ts

@@ -297,6 +297,9 @@ const getRuntimeSettingsAPI = () => getRegisteredRuntimeAPIs()?.settings ?? null
 
 const applyDesktopUiPreferences = (settings: DesktopSettings) => {
   const store = useUIStore.getState();
+  const configStore = typeof window !== 'undefined'
+    ? window.__zustand_config_store__?.getState?.() ?? null
+    : null;
   const queueStore = useMessageQueueStore.getState();
 
   if (typeof settings.showReasoningTraces === 'boolean' && settings.showReasoningTraces !== store.showReasoningTraces) {
@@ -407,6 +410,12 @@ const applyDesktopUiPreferences = (settings: DesktopSettings) => {
       store.setUserMessageRenderingMode(settings.userMessageRenderingMode);
     }
   }
+  if (typeof settings.messageStreamTransport === 'string'
+    && (settings.messageStreamTransport === 'auto' || settings.messageStreamTransport === 'ws' || settings.messageStreamTransport === 'sse')) {
+    if (configStore && settings.messageStreamTransport !== configStore.settingsMessageStreamTransport) {
+      configStore.setSettingsMessageStreamTransport(settings.messageStreamTransport);
+    }
+  }
   if (typeof settings.stickyUserHeader === 'boolean' && settings.stickyUserHeader !== store.stickyUserHeader) {
     store.setStickyUserHeader(settings.stickyUserHeader);
   }
@@ -804,6 +813,10 @@ const sanitizeWebSettings = (payload: unknown): DesktopSettings | null => {
     && (candidate.chatRenderMode === 'sorted' || candidate.chatRenderMode === 'live')) {
     result.chatRenderMode = candidate.chatRenderMode;
   }
+  if (typeof candidate.messageStreamTransport === 'string'
+    && (candidate.messageStreamTransport === 'auto' || candidate.messageStreamTransport === 'ws' || candidate.messageStreamTransport === 'sse')) {
+    result.messageStreamTransport = candidate.messageStreamTransport;
+  }
   if (typeof candidate.activityRenderMode === 'string'
     && (candidate.activityRenderMode === 'collapsed' || candidate.activityRenderMode === 'summary')) {
     result.activityRenderMode = candidate.activityRenderMode;