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/components/views/git/HistoryCommitRow.tsx

@@ -12,8 +12,6 @@ interface HistoryCommitRowProps {
   files: CommitFileEntry[];
   isLoadingFiles: boolean;
   onCopyHash: (hash: string) => void;
-  roundTop?: boolean;
-  roundBottom?: boolean;
 }
 
 function formatCommitDate(date: string) {
@@ -54,8 +52,6 @@ export const HistoryCommitRow: React.FC<HistoryCommitRowProps> = ({
   files,
   isLoadingFiles,
   onCopyHash,
-  roundTop = false,
-  roundBottom = false,
 }) => {
   return (
     <li>
@@ -64,8 +60,6 @@ export const HistoryCommitRow: React.FC<HistoryCommitRowProps> = ({
         onClick={onToggle}
         className={cn(
           'w-full flex items-start gap-3 px-3 py-2 text-left transition-colors',
-          roundTop && 'rounded-t-lg',
-          roundBottom && !isExpanded && 'rounded-b-lg',
           isExpanded ? 'bg-sidebar/90' : 'hover:bg-sidebar/40'
         )}
       >
@@ -113,7 +107,7 @@ export const HistoryCommitRow: React.FC<HistoryCommitRowProps> = ({
       </button>
 
       {isExpanded && (
-        <div className={cn('px-3 pb-2 pl-8 border-t border-border/40', roundBottom && 'rounded-b-lg')}>
+        <div className="px-3 pb-2 pl-8 border-t border-border/40">
           {isLoadingFiles ? (
             <div className="flex items-center gap-2 py-2">
               <RiLoader4Line className="size-4 animate-spin text-muted-foreground" />