Restructure frontend code to allow for extensions (#4721)

# Description of Changes
Move frontend code into `core` folder and add infrastructure for
`proprietary` folder to include premium, non-OSS features

frontend/src/core/components/layout/Workbench.css

@@ -0,0 +1,21 @@
+.workbench-scrollable {
+  overflow-y: auto !important;
+  overflow-x: hidden !important;
+}
+
+.workbench-scrollable::-webkit-scrollbar {
+  width: 0.375rem;
+}
+
+.workbench-scrollable::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+.workbench-scrollable::-webkit-scrollbar-thumb {
+  background-color: var(--mantine-color-gray-4);
+  border-radius: 0.1875rem;
+}
+
+.workbench-scrollable::-webkit-scrollbar-thumb:hover {
+  background-color: var(--mantine-color-gray-5);
+}

frontend/src/core/components/layout/Workbench.tsx

@@ -0,0 +1,196 @@
+import { Box } from '@mantine/core';
+import { useRainbowThemeContext } from '@app/components/shared/RainbowThemeProvider';
+import { useToolWorkflow } from '@app/contexts/ToolWorkflowContext';
+import { useFileHandler } from '@app/hooks/useFileHandler';
+import { useFileState } from '@app/contexts/FileContext';
+import { useNavigationState, useNavigationActions } from '@app/contexts/NavigationContext';
+import { isBaseWorkbench } from '@app/types/workbench';
+import { useViewer } from '@app/contexts/ViewerContext';
+import { useAppConfig } from '@app/contexts/AppConfigContext';
+import '@app/components/layout/Workbench.css';
+
+import TopControls from '@app/components/shared/TopControls';
+import FileEditor from '@app/components/fileEditor/FileEditor';
+import PageEditor from '@app/components/pageEditor/PageEditor';
+import PageEditorControls from '@app/components/pageEditor/PageEditorControls';
+import Viewer from '@app/components/viewer/Viewer';
+import LandingPage from '@app/components/shared/LandingPage';
+import Footer from '@app/components/shared/Footer';
+import DismissAllErrorsButton from '@app/components/shared/DismissAllErrorsButton';
+
+// No props needed - component uses contexts directly
+export default function Workbench() {
+  const { isRainbowMode } = useRainbowThemeContext();
+  const { config } = useAppConfig();
+
+  // Use context-based hooks to eliminate all prop drilling
+  const { selectors } = useFileState();
+  const { workbench: currentView } = useNavigationState();
+  const { actions: navActions } = useNavigationActions();
+  const setCurrentView = navActions.setWorkbench;
+  const activeFiles = selectors.getFiles();
+  const {
+    previewFile,
+    pageEditorFunctions,
+    sidebarsVisible,
+    setPreviewFile,
+    setPageEditorFunctions,
+    setSidebarsVisible,
+    customWorkbenchViews,
+  } = useToolWorkflow();
+
+  const { handleToolSelect } = useToolWorkflow();
+
+  // Get navigation state - this is the source of truth
+  const { selectedTool: selectedToolId } = useNavigationState();
+
+  // Get tool registry from context (instead of direct hook call)
+  const { toolRegistry } = useToolWorkflow();
+  const selectedTool = selectedToolId ? toolRegistry[selectedToolId] : null;
+  const { addFiles } = useFileHandler();
+
+  // Get active file index from ViewerContext
+  const { activeFileIndex, setActiveFileIndex } = useViewer();
+
+  const handlePreviewClose = () => {
+    setPreviewFile(null);
+    const previousMode = sessionStorage.getItem('previousMode');
+    if (previousMode === 'split') {
+      // Use context's handleToolSelect which coordinates tool selection and view changes
+      handleToolSelect('split');
+      sessionStorage.removeItem('previousMode');
+    } else if (previousMode === 'compress') {
+      handleToolSelect('compress');
+      sessionStorage.removeItem('previousMode');
+    } else if (previousMode === 'convert') {
+      handleToolSelect('convert');
+      sessionStorage.removeItem('previousMode');
+    } else {
+      setCurrentView('fileEditor');
+    }
+  };
+
+  const renderMainContent = () => {
+    if (activeFiles.length === 0) {
+      return (
+        <LandingPage
+        />
+      );
+    }
+
+    switch (currentView) {
+      case "fileEditor":
+        return (
+          <FileEditor
+            toolMode={!!selectedToolId}
+            supportedExtensions={selectedTool?.supportedFormats || ["pdf"]}
+            {...(!selectedToolId && {
+              onOpenPageEditor: () => {
+                setCurrentView("pageEditor");
+              },
+              onMergeFiles: (filesToMerge) => {
+                addFiles(filesToMerge);
+                setCurrentView("viewer");
+              }
+            })}
+          />
+        );
+
+      case "viewer":
+        return (
+          <Viewer
+            sidebarsVisible={sidebarsVisible}
+            setSidebarsVisible={setSidebarsVisible}
+            previewFile={previewFile}
+            onClose={handlePreviewClose}
+            activeFileIndex={activeFileIndex}
+            setActiveFileIndex={setActiveFileIndex}
+          />
+        );
+
+      case "pageEditor":
+        return (
+          <>
+            <PageEditor
+              onFunctionsReady={setPageEditorFunctions}
+            />
+            {pageEditorFunctions && (
+              <PageEditorControls
+                onClosePdf={pageEditorFunctions.closePdf}
+                onUndo={pageEditorFunctions.handleUndo}
+                onRedo={pageEditorFunctions.handleRedo}
+                canUndo={pageEditorFunctions.canUndo}
+                canRedo={pageEditorFunctions.canRedo}
+                onRotate={pageEditorFunctions.handleRotate}
+                onDelete={pageEditorFunctions.handleDelete}
+                onSplit={pageEditorFunctions.handleSplit}
+                onSplitAll={pageEditorFunctions.handleSplitAll}
+                onPageBreak={pageEditorFunctions.handlePageBreak}
+                onPageBreakAll={pageEditorFunctions.handlePageBreakAll}
+                onExportAll={pageEditorFunctions.onExportAll}
+                exportLoading={pageEditorFunctions.exportLoading}
+                selectionMode={pageEditorFunctions.selectionMode}
+                selectedPageIds={pageEditorFunctions.selectedPageIds}
+                displayDocument={pageEditorFunctions.displayDocument}
+                splitPositions={pageEditorFunctions.splitPositions}
+                totalPages={pageEditorFunctions.totalPages}
+              />
+            )}
+          </>
+        );
+
+      default:
+        if (!isBaseWorkbench(currentView)) {
+          const customView = customWorkbenchViews.find((view) => view.workbenchId === currentView && view.data != null);
+          if (customView) {
+            const CustomComponent = customView.component;
+            return <CustomComponent data={customView.data} />;
+          }
+        }
+        return <LandingPage />;
+    }
+  };
+
+  return (
+    <Box
+      className="flex-1 h-full min-w-80 relative flex flex-col"
+      data-tour="workbench"
+      style={
+        isRainbowMode
+          ? {} // No background color in rainbow mode
+          : { backgroundColor: 'var(--bg-background)' }
+      }
+    >
+      {/* Top Controls */}
+      {activeFiles.length > 0 && (
+        <TopControls
+          currentView={currentView}
+          setCurrentView={setCurrentView}
+          customViews={customWorkbenchViews}
+          activeFiles={activeFiles.map(f => {
+            const stub = selectors.getStirlingFileStub(f.fileId);
+            return { fileId: f.fileId, name: f.name, versionNumber: stub?.versionNumber };
+          })}
+          currentFileIndex={activeFileIndex}
+          onFileSelect={setActiveFileIndex}
+        />
+      )}
+
+      {/* Dismiss All Errors Button */}
+      <DismissAllErrorsButton />
+
+      {/* Main content area */}
+      <Box
+        className="flex-1 min-h-0 relative z-10 workbench-scrollable "
+        style={{
+          transition: 'opacity 0.15s ease-in-out',
+          paddingTop: currentView === 'viewer' ? '0' : (activeFiles.length > 0 ? '3.5rem' : '0'),
+        }}
+      >
+        {renderMainContent()}
+      </Box>
+
+      <Footer analyticsEnabled={config?.enableAnalytics === true} />
+    </Box>
+  );
+}