feat: hide workspace switcher when user has only 1 workspace

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/layout/AppShell.tsx

@@ -233,8 +233,8 @@ function Sidebar({
         )}
       </Box>
 
-      {/* Workspace tabs — side-by-side segmented control */}
-      <Box
+      {/* Workspace tabs — side-by-side segmented control (hidden when only 1 workspace) */}
+      {visibleWorkspaces.length > 1 && <Box
         sx={{
           borderBottom: `1px solid ${DIVIDER_COLOR}`,
           display: 'grid',
@@ -294,7 +294,7 @@ function Sidebar({
             <Box key={ws}>{tabContent}</Box>
           )
         })}
-      </Box>
+      </Box>}
 
       {/* Nav items */}
       <Box sx={{ flex: 1, overflowY: 'auto', py: 0.5 }}>