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/SyncActions.tsx

@@ -3,6 +3,7 @@ import {
   RiRefreshLine,
   RiArrowDownLine,
   RiArrowUpLine,
+  RiCloseLine,
   RiLoader4Line,
 } from '@remixicon/react';
 import { Button } from '@/components/ui/button';
@@ -23,7 +24,9 @@ interface SyncActionsProps {
   onFetch: (remote: GitRemote) => void;
   onPull: (remote: GitRemote) => void;
   onPush: () => void;
+  onRemoveRemote?: (remote: GitRemote) => void;
   disabled: boolean;
+  removingRemoteName?: string | null;
   iconOnly?: boolean;
   tooltipDelayMs?: number;
   aheadCount?: number;
@@ -36,14 +39,18 @@ export const SyncActions: React.FC<SyncActionsProps> = ({
   onFetch,
   onPull,
   onPush,
+  onRemoveRemote,
   disabled,
+  removingRemoteName = null,
   iconOnly = false,
   tooltipDelayMs = 1000,
   aheadCount = 0,
   behindCount = 0,
 }) => {
+  const skipRemoteSelectRef = React.useRef(false);
   const hasNoRemotes = remotes.length === 0;
-  const isDisabled = disabled || syncAction !== null || hasNoRemotes;
+  const isRemovingRemote = Boolean(removingRemoteName);
+  const isDisabled = disabled || syncAction !== null || isRemovingRemote || hasNoRemotes;
   const hasMultipleRemotes = remotes.length > 1;
 
   const handleFetch = () => {
@@ -145,14 +152,56 @@ export const SyncActions: React.FC<SyncActionsProps> = ({
         </Tooltip>
         <DropdownMenuContent align="start" className="min-w-[200px]">
           {remotes.map((remote) => (
-            <DropdownMenuItem key={remote.name} onSelect={() => onSelect(remote)}>
-              <div className="flex flex-col">
-                <span className="typography-ui-label text-foreground">
-                  {remote.name}
-                </span>
-                <span className="typography-meta text-muted-foreground truncate">
-                  {remote.fetchUrl}
-                </span>
+            <DropdownMenuItem
+              key={remote.name}
+              onSelect={(event) => {
+                if (skipRemoteSelectRef.current) {
+                  event.preventDefault();
+                  skipRemoteSelectRef.current = false;
+                  return;
+                }
+                onSelect(remote);
+              }}
+            >
+              <div className="flex w-full items-center gap-2">
+                <div className="min-w-0 flex-1">
+                  <div className="flex flex-col">
+                    <span className="typography-ui-label text-foreground">
+                      {remote.name}
+                    </span>
+                    <span className="typography-meta text-muted-foreground truncate">
+                      {remote.fetchUrl}
+                    </span>
+                  </div>
+                </div>
+                {onRemoveRemote ? (
+                  <Button
+                    type="button"
+                    variant="destructive"
+                    size="xs"
+                    className="h-6 w-6 px-0"
+                    disabled={syncAction !== null || isRemovingRemote}
+                    onPointerDown={(event) => {
+                      skipRemoteSelectRef.current = true;
+                      event.preventDefault();
+                      event.stopPropagation();
+                    }}
+                    onClick={(event) => {
+                      skipRemoteSelectRef.current = true;
+                      event.preventDefault();
+                      event.stopPropagation();
+                      onRemoveRemote(remote);
+                    }}
+                    aria-label={`Remove ${remote.name} remote`}
+                    title={`Remove ${remote.name}`}
+                  >
+                    {removingRemoteName === remote.name ? (
+                      <RiLoader4Line className="size-3.5 animate-spin" />
+                    ) : (
+                      <RiCloseLine className="size-3.5" />
+                    )}
+                  </Button>
+                ) : null}
               </div>
             </DropdownMenuItem>
           ))}