fix: tldraw user prefs colorScheme and indicator method for shape utils

- updateUserPreferences: isDarkMode → colorScheme ('dark'|'light') per
  tldraw 3.6.1 TLUserPreferences type (isDarkMode is read-only computed)
- BaseBoxShapeUtil subclasses: add required indicator() method returning
  bounding rect; fixes non-abstract class missing abstract member error

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

src/pages/exam/setup/ExamTemplateSetupPage.tsx

@@ -6,7 +6,7 @@ import ArrowBackIcon from '@mui/icons-material/ArrowBack'
 import SaveIcon from '@mui/icons-material/Save'
 import MouseIcon from '@mui/icons-material/Mouse'
 import '@tldraw/tldraw/tldraw.css'
-import { Editor, Tldraw, createShapeId, defaultBindingUtils, TLShape } from '@tldraw/tldraw'
+import { Editor, Tldraw, createShapeId, TLShape } from '@tldraw/tldraw'
 import axios from 'axios'
 
 import { ErrorBoundary } from '../../../components/ErrorBoundary'
@@ -17,7 +17,7 @@ import { ExamCanvasShapeModel, PAGE_HEIGHT, PAGE_WIDTH, isUuid, newDomainId, ser
 import { examCanvasShapeUtils, examCanvasTools, ExamCanvasTLShape, SHAPE_TYPES, shapeTypeToKind } from './examCanvasShapes'
 
 const TOOLS = [
-  { id: 'select', label: 'Select', tip: 'Move, resize, or delete shapes.', color: 'default' as const },
+  { id: 'select', label: 'Select', tip: 'Move, resize, or delete shapes.', color: 'inherit' as const },
   { id: SHAPE_TYPES.boundary, label: 'Boundary', tip: 'Draw one horizontal line. A main question is saved from each top+bottom pair.', color: 'error' as const },
   { id: SHAPE_TYPES.part, label: 'Part', tip: 'Draw the markable sub-question box inside a boundary pair.', color: 'warning' as const },
   { id: SHAPE_TYPES.response, label: 'Response', tip: 'Draw around where the student writes; saved with response_form=lines.', color: 'primary' as const },
@@ -25,7 +25,7 @@ const TOOLS = [
   { id: SHAPE_TYPES.question_number, label: 'Q Number', tip: 'Box the printed question number.', color: 'success' as const },
   { id: SHAPE_TYPES.mark_area, label: 'Mark Area', tip: 'Box printed marks such as [2].', color: 'success' as const },
   { id: SHAPE_TYPES.reference, label: 'Reference', tip: 'Box student resources/reference material.', color: 'info' as const },
-  { id: SHAPE_TYPES.furniture, label: 'Furniture', tip: 'Mark margins/page numbers/ignored decoration.', color: 'default' as const },
+  { id: SHAPE_TYPES.furniture, label: 'Furniture', tip: 'Mark margins/page numbers/ignored decoration.', color: 'inherit' as const },
 ]
 
 function apiMessage(err: unknown): { message: string; conflict: boolean } {
@@ -178,14 +178,13 @@ const ExamTemplateSetupInner: React.FC = () => {
       <Box sx={{ position: 'absolute', inset: 0, '& .tlui-layout': { display: 'none' } }} data-testid="exam-template-setup-canvas">
         <Tldraw
           shapeUtils={examCanvasShapeUtils as any}
-          bindingUtils={defaultBindingUtils}
           tools={examCanvasTools as any}
           hideUi
           inferDarkMode={theme.palette.mode === 'dark'}
           autoFocus
           onMount={(editor) => {
             editorRef.current = editor
-            editor.user.updateUserPreferences({ isDarkMode: theme.palette.mode === 'dark' })
+            editor.user.updateUserPreferences({ colorScheme: theme.palette.mode === 'dark' ? 'dark' : 'light' })
             editor.store.listen(() => setDirty(true), { scope: 'document' })
             if (template) loadShapes(editor, shapesFromTemplate(template)); else seedGuide(editor)
           }}

src/pages/exam/setup/examCanvasShapes.tsx

@@ -67,9 +67,11 @@ function defaultProps(kind: ExamCanvasShapeKind, w: number, h: number) {
   return { w, h, label: p.label, kind, responseForm: kind === 'response' ? 'lines' : undefined, contextType: kind === 'context' ? 'generic' : undefined }
 }
 
-class BoundaryUtil extends BaseBoxShapeUtil<ExamCanvasTLShape> { static override type = SHAPE_TYPES.boundary; static override props = { w: T.number, h: T.number, label: T.string, kind: T.string, maxMarks: T.optional(T.number), responseForm: T.optional(T.string), contextType: T.optional(T.string), questionId: T.optional(T.string), domainId: T.optional(T.string) }; override getDefaultProps(){ return defaultProps('boundary', 680, 8) }; override component(shape: ExamCanvasTLShape){ return renderShape(shape) } }
-class PartUtil extends BaseBoxShapeUtil<ExamCanvasTLShape> { static override type = SHAPE_TYPES.part; static override props = BoundaryUtil.props; override getDefaultProps(){ return defaultProps('part', 420, 170) }; override component(shape: ExamCanvasTLShape){ return renderShape(shape) } }
-function regionUtil(type: string, kind: ExamCanvasRegionKind, w = 360, h = 120) { return class extends BaseBoxShapeUtil<ExamCanvasTLShape> { static override type = type; static override props = BoundaryUtil.props; override getDefaultProps(){ return defaultProps(kind, w, h) }; override component(shape: ExamCanvasTLShape){ return renderShape(shape) } } }
+const sharedProps = { w: T.number, h: T.number, label: T.string, kind: T.string, maxMarks: T.optional(T.number), responseForm: T.optional(T.string), contextType: T.optional(T.string), questionId: T.optional(T.string), domainId: T.optional(T.string) }
+const ind = (s: ExamCanvasTLShape) => <rect width={toDomPrecision(s.props.w)} height={toDomPrecision(s.props.h)} />
+class BoundaryUtil extends BaseBoxShapeUtil<ExamCanvasTLShape> { static override type = SHAPE_TYPES.boundary; static override props = sharedProps; override getDefaultProps(){ return defaultProps('boundary', 680, 8) }; override component(shape: ExamCanvasTLShape){ return renderShape(shape) }; override indicator(shape: ExamCanvasTLShape){ return ind(shape) } }
+class PartUtil extends BaseBoxShapeUtil<ExamCanvasTLShape> { static override type = SHAPE_TYPES.part; static override props = sharedProps; override getDefaultProps(){ return defaultProps('part', 420, 170) }; override component(shape: ExamCanvasTLShape){ return renderShape(shape) }; override indicator(shape: ExamCanvasTLShape){ return ind(shape) } }
+function regionUtil(type: string, kind: ExamCanvasRegionKind, w = 360, h = 120) { return class extends BaseBoxShapeUtil<ExamCanvasTLShape> { static override type = type; static override props = sharedProps; override getDefaultProps(){ return defaultProps(kind, w, h) }; override component(shape: ExamCanvasTLShape){ return renderShape(shape) }; override indicator(shape: ExamCanvasTLShape){ return ind(shape) } } }
 
 class BoundaryTool extends BaseBoxShapeTool { static override id = SHAPE_TYPES.boundary; static override initial = 'pointing'; shapeType = SHAPE_TYPES.boundary }
 class PartTool extends BaseBoxShapeTool { static override id = SHAPE_TYPES.part; static override initial = 'pointing'; shapeType = SHAPE_TYPES.part }