feature: header layout changes (#195)

* fix(ui): remove fixed sessions button and mac titlebar coupling

Remove fixed sessions button from header on desktop Mac
Eliminate Mac titlebar spacer and drag-to-dock logic in sidebar
Update layout to rely on standard header/sidebar without mac-specific tweaks

* feat: improve mobile header with session toggle and back button

Add back button in mobile header to exit session switcher
Show Sessions label when session switcher is open in mobile header
Toggle between opening sessions and back navigation based on session state

packages/ui/src/components/layout/Sidebar.tsx

@@ -11,7 +11,6 @@ import { Tooltip, TooltipContent, TooltipTrigger } from '../ui/tooltip';
 export const SIDEBAR_CONTENT_WIDTH = 264;
 const SIDEBAR_MIN_WIDTH = 200;
 const SIDEBAR_MAX_WIDTH = 500;
-const MAC_TITLEBAR_SAFE_AREA = 40;
 const CHECK_FOR_UPDATES_EVENT = 'openchamber:check-for-updates';
 
 interface SidebarProps {
@@ -40,12 +39,7 @@ export const Sidebar: React.FC<SidebarProps> = ({ isOpen, isMobile, children })
         return typeof (window as typeof window & { opencodeDesktop?: unknown }).opencodeDesktop !== 'undefined';
     });
 
-    const isMacPlatform = React.useMemo(() => {
-        if (typeof navigator === 'undefined') {
-            return false;
-        }
-        return /Macintosh|Mac OS X/.test(navigator.userAgent || '');
-    }, []);
+
 
     React.useEffect(() => {
         if (typeof window === 'undefined') {
@@ -127,23 +121,6 @@ export const Sidebar: React.FC<SidebarProps> = ({ isOpen, isMobile, children })
         }
     }, [isMobile, isResizing]);
 
-    const handleTitlebarDragStart = React.useCallback(async (e: React.MouseEvent) => {
-
-        if (e.button !== 0) {
-            return;
-        }
-
-        if (isDesktopApp) {
-            try {
-                const { getCurrentWindow } = await import('@tauri-apps/api/window');
-                const window = getCurrentWindow();
-                await window.startDragging();
-            } catch (error) {
-                console.error('Failed to start window dragging from sidebar:', error);
-            }
-        }
-    }, [isDesktopApp]);
-
     if (isMobile) {
 
         return null;
@@ -153,7 +130,6 @@ export const Sidebar: React.FC<SidebarProps> = ({ isOpen, isMobile, children })
         SIDEBAR_MAX_WIDTH,
         Math.max(SIDEBAR_MIN_WIDTH, sidebarWidth || SIDEBAR_CONTENT_WIDTH)
     ) : 0;
-    const shouldRenderTitlebarSpacer = isDesktopApp && isMacPlatform;
 
     const handlePointerDown = (event: React.PointerEvent) => {
         if (!isOpen) {
@@ -203,14 +179,6 @@ export const Sidebar: React.FC<SidebarProps> = ({ isOpen, isMobile, children })
                 style={{ width: `${appliedWidth}px`, overflowX: 'hidden' }}
                 aria-hidden={!isOpen}
             >
-                {shouldRenderTitlebarSpacer && (
-                    <div
-                        className="flex-shrink-0 select-none"
-                        style={{ height: `${MAC_TITLEBAR_SAFE_AREA}px` }}
-                        onMouseDown={handleTitlebarDragStart}
-                        aria-hidden
-                    />
-                )}
                 <div className="flex-1 overflow-hidden">
                     <ErrorBoundary>{children}</ErrorBoundary>
                 </div>