Refactor to use MutableRefObject instead of RefObject

Replaces all instances of React.RefObject with React.MutableRefObject for refs that are mutated directly throughout the codebase. This change clarifies intent and improves type safety for refs that are updated outside of React's ref assignment.

frontend/src/components/pageEditor/PageThumbnail.tsx

@@ -23,7 +23,7 @@ interface PageThumbnailProps {
   selectionMode: boolean;
   movingPage: number | null;
   isAnimating: boolean;
-  pageRefs: React.RefObject<Map<string, HTMLDivElement>>;
+  pageRefs: React.MutableRefObject<Map<string, HTMLDivElement>>;
   onReorderPages: (sourcePageNumber: number, targetIndex: number, selectedPageIds?: string[]) => void;
   onTogglePage: (pageId: string) => void;
   onAnimateReorder: () => void;

frontend/src/components/tools/ToolPicker.tsx

@@ -71,7 +71,7 @@ const ToolPicker = ({ selectedToolKey, onSelect, filteredTools, isSearching = fa
     [visibleSections]
   );
 
-  const scrollTo = (ref: React.RefObject<HTMLDivElement | null>) => {
+  const scrollTo = (ref: React.MutableRefObject<HTMLDivElement | null>) => {
     const container = scrollableRef.current;
     const target = ref.current;
     if (container && target) {

frontend/src/contexts/FileManagerContext.tsx

@@ -13,7 +13,7 @@ interface FileManagerContextValue {
   searchTerm: string;
   selectedFiles: StirlingFileStub[];
   filteredFiles: StirlingFileStub[];
-  fileInputRef: React.RefObject<HTMLInputElement | null>;
+  fileInputRef: React.MutableRefObject<HTMLInputElement | null>;
   selectedFilesSet: Set<FileId>;
   expandedFileIds: Set<FileId>;
   fileGroups: Map<FileId, StirlingFileStub[]>;

frontend/src/contexts/file/fileActions.ts

@@ -165,8 +165,8 @@ interface AddFileOptions {
  */
 export async function addFiles(
   options: AddFileOptions,
-  stateRef: React.RefObject<FileContextState>,
-  filesRef: React.RefObject<Map<FileId, File>>,
+  stateRef: React.MutableRefObject<FileContextState>,
+  filesRef: React.MutableRefObject<Map<FileId, File>>,
   dispatch: React.Dispatch<FileContextAction>,
   lifecycleManager: FileLifecycleManager,
   enablePersistence: boolean = false
@@ -278,7 +278,7 @@ export async function consumeFiles(
   inputFileIds: FileId[],
   outputStirlingFiles: StirlingFile[],
   outputStirlingFileStubs: StirlingFileStub[],
-  filesRef: React.RefObject<Map<FileId, File>>,
+  filesRef: React.MutableRefObject<Map<FileId, File>>,
   dispatch: React.Dispatch<FileContextAction>
 ): Promise<FileId[]> {
   if (DEBUG) console.log(`📄 consumeFiles: Processing ${inputFileIds.length} input files, ${outputStirlingFiles.length} output files with pre-created stubs`);
@@ -357,7 +357,7 @@ export async function consumeFiles(
 async function restoreFilesAndCleanup(
   filesToRestore: { file: File; record: StirlingFileStub }[],
   fileIdsToRemove: FileId[],
-  filesRef: React.RefObject<Map<FileId, File>>,
+  filesRef: React.MutableRefObject<Map<FileId, File>>,
   indexedDB?: { deleteFile: (fileId: FileId) => Promise<void> } | null
 ): Promise<void> {
   // Remove files from filesRef
@@ -406,7 +406,7 @@ export async function undoConsumeFiles(
   inputFiles: File[],
   inputStirlingFileStubs: StirlingFileStub[],
   outputFileIds: FileId[],
-  filesRef: React.RefObject<Map<FileId, File>>,
+  filesRef: React.MutableRefObject<Map<FileId, File>>,
   dispatch: React.Dispatch<FileContextAction>,
   indexedDB?: { saveFile: (file: File, fileId: FileId, existingThumbnail?: string) => Promise<any>; deleteFile: (fileId: FileId) => Promise<void> } | null
 ): Promise<void> {
@@ -468,8 +468,8 @@ export async function undoConsumeFiles(
 export async function addStirlingFileStubs(
   stirlingFileStubs: StirlingFileStub[],
   options: { insertAfterPageId?: string; selectFiles?: boolean } = {},
-  stateRef: React.RefObject<FileContextState>,
-  filesRef: React.RefObject<Map<FileId, File>>,
+  stateRef: React.MutableRefObject<FileContextState>,
+  filesRef: React.MutableRefObject<Map<FileId, File>>,
   dispatch: React.Dispatch<FileContextAction>,
   _lifecycleManager: FileLifecycleManager
 ): Promise<StirlingFile[]> {

frontend/src/contexts/file/fileSelectors.ts

@@ -15,8 +15,8 @@ import {
  * Create stable selectors using stateRef and filesRef
  */
 export function createFileSelectors(
-  stateRef: React.RefObject<FileContextState>,
-  filesRef: React.RefObject<Map<FileId, File>>
+  stateRef: React.MutableRefObject<FileContextState>,
+  filesRef: React.MutableRefObject<Map<FileId, File>>
 ): FileContextSelectors {
   return {
     getFile: (id: FileId) => {
@@ -125,8 +125,8 @@ export function buildQuickKeySetFromMetadata(metadata: { name: string; size: num
  * Get primary file (first in list) - commonly used pattern
  */
 export function getPrimaryFile(
-  stateRef: React.RefObject<FileContextState>,
-  filesRef: React.RefObject<Map<FileId, File>>
+  stateRef: React.MutableRefObject<FileContextState>,
+  filesRef: React.MutableRefObject<Map<FileId, File>>
 ): { file?: File; record?: StirlingFileStub } {
   const primaryFileId = stateRef.current.files.ids[0];
   if (!primaryFileId) return {};

frontend/src/contexts/file/lifecycle.ts

@@ -16,7 +16,7 @@ export class FileLifecycleManager {
   private fileGenerations = new Map<string, number>(); // Generation tokens to prevent stale cleanup
 
   constructor(
-    private filesRef: React.RefObject<Map<FileId, File>>,
+    private filesRef: React.MutableRefObject<Map<FileId, File>>,
     private dispatch: React.Dispatch<FileContextAction>
   ) {}
 
@@ -34,7 +34,7 @@ export class FileLifecycleManager {
   /**
    * Clean up resources for a specific file (with stateRef access for complete cleanup)
    */
-  cleanupFile = (fileId: FileId, stateRef?: React.RefObject<any>): void => {
+  cleanupFile = (fileId: FileId, stateRef?: React.MutableRefObject<any>): void => {
     // Use comprehensive cleanup (same as removeFiles)
     this.cleanupAllResourcesForFile(fileId, stateRef);
 
@@ -68,7 +68,7 @@ export class FileLifecycleManager {
   /**
    * Schedule delayed cleanup for a file with generation token to prevent stale cleanup
    */
-  scheduleCleanup = (fileId: FileId, delay: number = 30000, stateRef?: React.RefObject<any>): void => {
+  scheduleCleanup = (fileId: FileId, delay: number = 30000, stateRef?: React.MutableRefObject<any>): void => {
     // Cancel existing timer
     const existingTimer = this.cleanupTimers.get(fileId);
     if (existingTimer) {
@@ -101,7 +101,7 @@ export class FileLifecycleManager {
   /**
    * Remove a file immediately with complete resource cleanup
    */
-  removeFiles = (fileIds: FileId[], stateRef?: React.RefObject<any>): void => {
+  removeFiles = (fileIds: FileId[], stateRef?: React.MutableRefObject<any>): void => {
     fileIds.forEach(fileId => {
       // Clean up all resources for this file
       this.cleanupAllResourcesForFile(fileId, stateRef);
@@ -114,7 +114,7 @@ export class FileLifecycleManager {
   /**
    * Complete resource cleanup for a single file
    */
-  private cleanupAllResourcesForFile = (fileId: FileId, stateRef?: React.RefObject<any>): void => {
+  private cleanupAllResourcesForFile = (fileId: FileId, stateRef?: React.MutableRefObject<any>): void => {
     // Remove from files ref
     this.filesRef.current.delete(fileId);
 
@@ -166,7 +166,7 @@ export class FileLifecycleManager {
   /**
    * Update file record with race condition guards
    */
-  updateStirlingFileStub = (fileId: FileId, updates: Partial<StirlingFileStub>, stateRef?: React.RefObject<any>): void => {
+  updateStirlingFileStub = (fileId: FileId, updates: Partial<StirlingFileStub>, stateRef?: React.MutableRefObject<any>): void => {
     // Guard against updating removed files (race condition protection)
     if (!this.filesRef.current.has(fileId)) {
       if (DEBUG) console.warn(`🗂️ Attempted to update removed file (filesRef): ${fileId}`);

frontend/src/hooks/useIsOverflowing.ts

@@ -32,7 +32,7 @@ import * as React from 'react';
 */
 
 
-export const useIsOverflowing = (ref: React.RefObject<HTMLElement | null>, callback?: (isOverflow: boolean) => void) => {
+export const useIsOverflowing = (ref: React.MutableRefObject<HTMLElement | null>, callback?: (isOverflow: boolean) => void) => {
   // State to track overflow status
   const [isOverflow, setIsOverflow] = React.useState<boolean | undefined>(undefined);
 

frontend/src/hooks/useTooltipPosition.ts

@@ -60,8 +60,8 @@ export function useTooltipPosition({
   sidebarTooltip: boolean;
   position: Position;
   gap: number;
-  triggerRef: React.RefObject<HTMLElement | null>;
-  tooltipRef: React.RefObject<HTMLDivElement | null>;
+  triggerRef: React.MutableRefObject<HTMLElement | null>;
+  tooltipRef: React.MutableRefObject<HTMLDivElement | null>;
   sidebarRefs?: SidebarRefs;
   sidebarState?: SidebarState;
 }): PositionState {

frontend/src/types/sidebar.ts

@@ -5,8 +5,8 @@ export interface SidebarState {
 }
 
 export interface SidebarRefs {
-  quickAccessRef: React.RefObject<HTMLDivElement | null>;
-  toolPanelRef: React.RefObject<HTMLDivElement | null>;
+  quickAccessRef: React.MutableRefObject<HTMLDivElement | null>;
+  toolPanelRef: React.MutableRefObject<HTMLDivElement | null>;
 }
 
 export interface SidebarInfo {