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/vscode/src/bridge.ts

@@ -3399,12 +3399,30 @@ export async function handleBridgeMessage(message: BridgeRequest, ctx?: BridgeCo
       }
 
       case 'api:git/remotes': {
-        const { directory } = (payload || {}) as { directory?: string };
+        const { directory, method, remote } = (payload || {}) as {
+          directory?: string;
+          method?: string;
+          remote?: string;
+        };
         if (!directory) {
           return { id, type, success: false, error: 'Directory is required' };
         }
-        const result = await gitService.getRemotes(directory);
-        return { id, type, success: true, data: result };
+
+        const normalizedMethod = typeof method === 'string' ? method.toUpperCase() : 'GET';
+        if (normalizedMethod === 'GET') {
+          const result = await gitService.getRemotes(directory);
+          return { id, type, success: true, data: result };
+        }
+
+        if (normalizedMethod === 'DELETE') {
+          if (!remote) {
+            return { id, type, success: false, error: 'Remote name is required' };
+          }
+          const result = await gitService.removeRemote(directory, remote);
+          return { id, type, success: true, data: result };
+        }
+
+        return { id, type, success: false, error: `Unsupported method: ${normalizedMethod}` };
       }
 
       case 'api:git/rebase': {

packages/vscode/src/gitService.ts

@@ -2576,6 +2576,23 @@ export async function getRemotes(directory: string): Promise<GitRemote[]> {
   return Array.from(remoteMap.values());
 }
 
+export async function removeRemote(directory: string, remote: string): Promise<{ success: boolean }> {
+  const remoteName = String(remote || '').trim();
+  if (!remoteName) {
+    throw new Error('Remote name is required');
+  }
+  if (remoteName === 'origin') {
+    throw new Error('Cannot remove origin remote');
+  }
+
+  const result = await execGit(['remote', 'remove', remoteName], directory);
+  if (result.exitCode !== 0) {
+    throw new Error(result.stderr || result.stdout || `Failed to remove remote ${remoteName}`);
+  }
+
+  return { success: true };
+}
+
 // ============== Merge & Rebase Operations ==============
 
 export interface GitMergeResult {