Major UI refresh: sidebar redesign, theme expansion, and chat performance optimizations (#706)

## Summary
Complete sidebar redesign and comprehensive UI polish pass with performance optimizations, theme system refinements, and desktop integration improvements.

## Key Changes

**Sidebar & Navigation Redesign**
- Redesigned sessions sidebar layout with unified button primitives
- Added activity sections with project grouping and improved session organization
- Refined sidebar corners, spacing, and visual hierarchy
- Removed NavRail component in favor of streamlined sidebar
- Stabilized sessions bar toggle position in fullscreen mode

**Performance Optimizations**
- Reduced chat streaming CPU usage and storage churn
- Optimized task tool polling and live timers with debouncing
- Prevented chat state races and reduced background request load
- Debounced draft writes and coalesced session reloads
- Optimized message store updates and turn tracking

**Theme & Visual System**
- Added theme-aware window corners (desktop) and border radius tokens
- Introduced glassmorphism effects on desktop sidebar
- Added backdrop blur to UI elements

**Chat Experience**
- Added session-based permission auto-accept toggle in chat input
- Polished permission shield UX with improved icon sizing and spacing
- Fixed chat scroll-to-bottom behavior and timeline tracking
- Enhanced tool output display with better path label detection
- Removed duplicate draft context details in chat header
- Added text selection menu to chat messages

**Git Improvements**
- Refreshed git history visual design with cleaner dividers
- Added remote removal action in sync selector
- Stabilized git polling to prevent excessive requests
- Improved tool output rendering for git operations

**Settings & Panels**
- Fixed mobile scrolling on settings pages
- Made outside-click settings close instantly
- Reduced settings load churn and CPU spikes
- Improved services dropdown layout and spacing
- Softened panel resize handles

**Desktop Integration**
- Synced macOS window theme with app theme
- Restored window dragging in sidebar header zones
- Fixed system window corners on macOS
- Improved header session metadata and action controls

**Button & Component Standardization**
- Unified button primitives across all components
- Standardized destructive action patterns
- Removed unused button variants (button-large, button-small)
- Aligned context tab close hit areas

---------

Co-authored-by: Iuliia Ivashko <yulia.ivashko@gmail.com>

packages/ui/src/stores/useSessionFoldersStore.ts

@@ -49,6 +49,10 @@ const safeStorage = getSafeStorage();
 let diskWriteTimer: ReturnType<typeof setTimeout> | null = null;
 let diskHydrated = false;
 let diskHydrationInFlight = false;
+let persistFoldersTimer: ReturnType<typeof setTimeout> | undefined;
+let persistCollapsedTimer: ReturnType<typeof setTimeout> | undefined;
+let pendingFoldersMap: SessionFoldersMap | null = null;
+let pendingCollapsedIds: Set<string> | null = null;
 
 const isVSCodeWebview = (): boolean => {
   if (typeof window === 'undefined') {
@@ -185,21 +189,50 @@ const readPersistedCollapsed = (): Set<string> => {
 };
 
 const persistFolders = (foldersMap: SessionFoldersMap): void => {
-  try {
-    safeStorage.setItem(FOLDERS_STORAGE_KEY, JSON.stringify(foldersMap));
-  } catch {
-    // ignored
-  }
+  pendingFoldersMap = foldersMap;
+  clearTimeout(persistFoldersTimer);
+  persistFoldersTimer = setTimeout(() => {
+    try {
+      safeStorage.setItem(FOLDERS_STORAGE_KEY, JSON.stringify(foldersMap));
+      pendingFoldersMap = null;
+    } catch {
+      // ignored
+    }
+  }, 300);
 };
 
 const persistCollapsed = (collapsedFolderIds: Set<string>): void => {
-  try {
-    safeStorage.setItem(COLLAPSED_STORAGE_KEY, JSON.stringify(Array.from(collapsedFolderIds)));
-  } catch {
-    // ignored
-  }
+  pendingCollapsedIds = collapsedFolderIds;
+  clearTimeout(persistCollapsedTimer);
+  persistCollapsedTimer = setTimeout(() => {
+    try {
+      safeStorage.setItem(COLLAPSED_STORAGE_KEY, JSON.stringify(Array.from(collapsedFolderIds)));
+      pendingCollapsedIds = null;
+    } catch {
+      // ignored
+    }
+  }, 300);
 };
 
+if (typeof window !== 'undefined') {
+  window.addEventListener('beforeunload', () => {
+    if (pendingFoldersMap !== null) {
+      clearTimeout(persistFoldersTimer);
+      try {
+        safeStorage.setItem(FOLDERS_STORAGE_KEY, JSON.stringify(pendingFoldersMap));
+      } catch { /* ignored */ }
+      pendingFoldersMap = null;
+    }
+    if (pendingCollapsedIds !== null) {
+      clearTimeout(persistCollapsedTimer);
+      try {
+        safeStorage.setItem(COLLAPSED_STORAGE_KEY, JSON.stringify(Array.from(pendingCollapsedIds)));
+      } catch { /* ignored */ }
+      pendingCollapsedIds = null;
+    }
+  });
+}
+
 const persistState = (foldersMap: SessionFoldersMap, collapsedFolderIds: Set<string>): void => {
   persistFolders(foldersMap);
   persistCollapsed(collapsedFolderIds);