feat(ui): redesign workspace shell with context panel, tabbed sidebars, and faster diff UX (#433)

* feat: tabbed right sidebar, context panel, floating diff comments

* fix: auto-close left sidebar when context panel opens

- Increase default context panel width from 520 to 600 pixels
- Increase sidebar minimum width from 200 to 300 pixels
- Replace collapsible component with custom button in diff view

* refactoring: rework sidebars, tabs, and file tree layout

- Rewrite AnimatedTabs as segment-style with sliding indicator
- Upgrade SidebarFilesTree to match FilesView features (context menus,
  git status, file icons, CRUD dialogs, fuzzy search ranking)
- Restructure FilesView header: tabs row + actions row, remove breadcrumbs
- Show relative path in context panel header, track active tab
- Allow left sidebar to stay open alongside context panel
- Hide diff/files tabs from header on desktop (mobile-only)
- Move chevron after group name in session sidebar
- Compact tab heights in right sidebar and git view
- Size PreviewToggleButton to match other action buttons
- Remove directory loading spinner from folder icons

* feat: add project icon and color customization

- Enable users to assign custom icons to projects
- Allow users to choose accent colors for projects
- Stabilize repo status UI during project switching

* feat: add scroll fade indicators to editor tabs

* style: reduce spacing and icon sizes in header

* style: adjust tab component padding from uniform to vertical-horizontal

* feat: Add session state indicators to project tabs

* feat: Enhance session status handling and improve UI responsiveness

* fix: preserve upstream tracking on branch rename

* fix: improve initial remote selection for pull requests

- Uses saved remote name from previous session when available
- Selects remote based on tracking branch when possible
- Falls back to origin or first available remote

* perf(diff): faster highlight, stable stacked scroll

- split/unified Pierre worker pools; prefer shiki-wasm
- align diff CSS line-height; disable scroll anchoring; drop WebKit compositing hacks
- harden stacked pin/align (cancel on user scroll/input); prevent overscroll
- make overlay scrollbar MutationObserver optional; disable for diff container

* feat: handle binary files in diff view

* fix: adjust project tabs layout and drag regions

* style: update drag overlay visual styling

* feat: enable number keys to switch projects in the sidebar

* fix: recognize octet-stream as text-based MIME type

* feat: add keyboard navigation to context panel

* feat: add session pinning to sidebar

- Pin important sessions to keep them at the top
- Pinned sessions persist across browser sessions

* refactor: move context usage display from chat input to header

packages/ui/src/components/views/GitView.tsx

@@ -1640,7 +1640,7 @@ export const GitView: React.FC<GitViewProps> = ({ mode = 'full' }) => {
         isWorktreeMode={!!worktreeMetadata}
         isSidebarMode={isSidebarMode}
         onOpenHistory={() => setIsHistoryDialogOpen(true)}
-        onOpenBranchPicker={branchPickerProject ? () => setIsBranchPickerOpen(true) : undefined}
+        onOpenBranchPicker={!isSidebarMode && branchPickerProject ? () => setIsBranchPickerOpen(true) : undefined}
       />
 
       {/* In-progress operation banner */}
@@ -1662,10 +1662,11 @@ export const GitView: React.FC<GitViewProps> = ({ mode = 'full' }) => {
       <div className="flex-1 min-h-0 overflow-hidden">
         <div className="h-full min-h-0 flex flex-col">
           <div className={cn('min-w-0 min-h-0 h-full bg-muted/10 flex flex-col', isSidebarMode && 'border-t border-border/40')}>
-            <div className="px-3 py-3">
+            <div className="px-3 py-1.5">
               <AnimatedTabs<ActionTab>
                 value={actionTab}
                 onValueChange={setActionTab}
+                size="sm"
                 collapseLabelsOnSmall
                 collapseLabelsOnNarrow={isSidebarMode}
                 tabs={[
@@ -1700,7 +1701,13 @@ export const GitView: React.FC<GitViewProps> = ({ mode = 'full' }) => {
                         onToggleFile={toggleFileSelection}
                         onSelectAll={selectAll}
                         onClearSelection={clearSelection}
-                        onViewDiff={(path) => useUIStore.getState().navigateToDiff(path)}
+                        onViewDiff={(path) => {
+                          if (isSidebarMode && currentDirectory) {
+                            useUIStore.getState().openContextDiff(currentDirectory, path);
+                            return;
+                          }
+                          useUIStore.getState().navigateToDiff(path);
+                        }}
                         onRevertFile={handleRevertFile}
                       />
 
@@ -1793,6 +1800,7 @@ export const GitView: React.FC<GitViewProps> = ({ mode = 'full' }) => {
                     directory={pullRequestProps.directory}
                     branch={pullRequestProps.branch}
                     baseBranch={baseBranch}
+                    trackingBranch={status?.tracking ?? undefined}
                     remotes={remotes}
                     remoteBranches={remoteBranches}
                     onGeneratedDescription={scrollActionPanelToBottom}