Frontend V2 Ui Tweaks (#4590)

* Top Controls only show when files > 0
* Moved content down so top controls don't obscure
* Viewer background set to match workbench and shadow around pages added
so that page boundaries are visible
* unsaved-changes modal rework

---------

Co-authored-by: Connor Yoh <[email protected]>

frontend/src/components/layout/Workbench.tsx

@@ -146,10 +146,12 @@ export default function Workbench() {
       }
     >
       {/* Top Controls */}
-      <TopControls
-        currentView={currentView}
-        setCurrentView={setCurrentView}
-      />
+      {activeFiles.length > 0 && (
+        <TopControls
+          currentView={currentView}
+          setCurrentView={setCurrentView}
+        />
+      )}
 
       {/* Dismiss All Errors Button */}
       <DismissAllErrorsButton />
@@ -159,6 +161,7 @@ export default function Workbench() {
         className="flex-1 min-h-0 relative z-10 workbench-scrollable "
         style={{
           transition: 'opacity 0.15s ease-in-out',
+          paddingTop: activeFiles.length > 0 ? '3.5rem' : '0',
         }}
       >
         {renderMainContent()}