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/useMcpConfigStore.ts

@@ -72,6 +72,14 @@ export const envArrayToRecord = (arr: Array<{ key: string; value: string }>): Re
 };
 
 const CLIENT_RELOAD_DELAY_MS = 800;
+const MCP_LOAD_CACHE_TTL_MS = 5000;
+const DEFAULT_MCP_CACHE_KEY = '__default__';
+const mcpLastLoadedAt = new Map<string, number>();
+const mcpLoadInFlight = new Map<string, Promise<boolean>>();
+
+const getMcpCacheKey = (directory: string | null): string => {
+  return directory?.trim() || DEFAULT_MCP_CACHE_KEY;
+};
 
 // ============== STORE ==============
 
@@ -104,23 +112,47 @@ export const useMcpConfigStore = create<McpConfigStore>()(
         setMcpDraft: (draft) => set({ mcpDraft: draft }),
 
         loadMcpConfigs: async () => {
-          set({ isLoading: true });
-          try {
-            const configDirectory = getConfigDirectory();
-            const queryParams = configDirectory ? `?directory=${encodeURIComponent(configDirectory)}` : '';
-            const response = await fetch(`/api/config/mcp${queryParams}`, {
-              headers: configDirectory ? { 'x-opencode-directory': configDirectory } : undefined,
-            });
-            if (!response.ok) {
-              throw new Error('Failed to load MCP configs');
-            }
-            const data: McpServerWithScope[] = await response.json();
-            set({ mcpServers: data, isLoading: false });
+          const configDirectory = getConfigDirectory();
+          const cacheKey = getMcpCacheKey(configDirectory);
+          const now = Date.now();
+          const loadedAt = mcpLastLoadedAt.get(cacheKey) ?? 0;
+          const hasCachedConfigs = get().mcpServers.length > 0;
+
+          if (hasCachedConfigs && now - loadedAt < MCP_LOAD_CACHE_TTL_MS) {
             return true;
-          } catch (error) {
-            console.error('[McpConfigStore] Failed to load MCP configs:', error);
-            set({ isLoading: false });
-            return false;
+          }
+
+          const inFlight = mcpLoadInFlight.get(cacheKey);
+          if (inFlight) {
+            return inFlight;
+          }
+
+          const request = (async () => {
+            set({ isLoading: true });
+            try {
+              const queryParams = configDirectory ? `?directory=${encodeURIComponent(configDirectory)}` : '';
+              const response = await fetch(`/api/config/mcp${queryParams}`, {
+                headers: configDirectory ? { 'x-opencode-directory': configDirectory } : undefined,
+              });
+              if (!response.ok) {
+                throw new Error('Failed to load MCP configs');
+              }
+              const data: McpServerWithScope[] = await response.json();
+              set({ mcpServers: data, isLoading: false });
+              mcpLastLoadedAt.set(cacheKey, Date.now());
+              return true;
+            } catch (error) {
+              console.error('[McpConfigStore] Failed to load MCP configs:', error);
+              set({ isLoading: false });
+              return false;
+            }
+          })();
+
+          mcpLoadInFlight.set(cacheKey, request);
+          try {
+            return await request;
+          } finally {
+            mcpLoadInFlight.delete(cacheKey);
           }
         },