fix: PDF generation now respects operator and digitRange settings

The PDF generation route was ignoring the operator and digitRange settings,
always generating 2-digit addition problems regardless of configuration.
The preview worked correctly but PDF generation was broken.

Changes:
- Add conditional logic to call appropriate problem generator based on operator
- Pass digitRange parameter to all problem generators
- Add generatePlaceValueColors() to Typst template for color definitions
- Import DisplayOptions type for internal use in typstHelpers

Fixes worksheet PDF generation for subtraction, mixed, and multi-digit problems.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/app/api/create/worksheets/addition/route.ts

@@ -3,9 +3,13 @@
 import { type NextRequest, NextResponse } from 'next/server'
 import { execSync } from 'child_process'
 import { validateWorksheetConfig } from '@/app/create/worksheets/addition/validation'
-import { generateProblems } from '@/app/create/worksheets/addition/problemGenerator'
+import {
+  generateProblems,
+  generateSubtractionProblems,
+  generateMixedProblems,
+} from '@/app/create/worksheets/addition/problemGenerator'
 import { generateTypstSource } from '@/app/create/worksheets/addition/typstGenerator'
-import type { WorksheetFormState } from '@/app/create/worksheets/addition/types'
+import type { WorksheetFormState, WorksheetProblem } from '@/app/create/worksheets/addition/types'
 
 export async function POST(request: NextRequest) {
   try {
@@ -22,14 +26,37 @@ export async function POST(request: NextRequest) {
 
     const config = validation.config
 
-    // Generate problems
-    const problems = generateProblems(
-      config.total,
-      config.pAnyStart,
-      config.pAllStart,
-      config.interpolate,
-      config.seed
-    )
+    // Generate problems based on operator type
+    let problems: WorksheetProblem[]
+    if (config.operator === 'addition') {
+      problems = generateProblems(
+        config.total,
+        config.pAnyStart,
+        config.pAllStart,
+        config.interpolate,
+        config.seed,
+        config.digitRange
+      )
+    } else if (config.operator === 'subtraction') {
+      problems = generateSubtractionProblems(
+        config.total,
+        config.digitRange,
+        config.pAnyStart,
+        config.pAllStart,
+        config.interpolate,
+        config.seed
+      )
+    } else {
+      // mixed
+      problems = generateMixedProblems(
+        config.total,
+        config.digitRange,
+        config.pAnyStart,
+        config.pAllStart,
+        config.interpolate,
+        config.seed
+      )
+    }
 
     // Generate Typst sources (one per page)
     const typstSources = generateTypstSource(config, problems)

apps/web/src/app/create/worksheets/addition/typstGenerator.ts

@@ -5,6 +5,7 @@ import {
   generateTypstHelpers,
   generateProblemStackFunction,
   generateSubtractionProblemStackFunction,
+  generatePlaceValueColors,
 } from './typstHelpers'
 import { analyzeProblem, analyzeSubtractionProblem } from './problemAnalysis'
 import { resolveDisplayForProblem } from './displayRules'
@@ -185,6 +186,8 @@ function generatePageTypst(
         : 'false'
   }
 
+${generatePlaceValueColors()}
+
 ${generateTypstHelpers(cellSize)}
 
 ${generateProblemStackFunction(cellSize, maxDigits)}

apps/web/src/app/create/worksheets/addition/typstHelpers.ts

@@ -4,6 +4,9 @@
 // NOTE: This file now re-exports from the modular typstHelpers/ directory
 // for backward compatibility. New code should import from typstHelpers/ directly.
 
+// Import types for internal use
+import type { DisplayOptions } from './typstHelpers/shared/types'
+
 // Re-export everything from modular structure
 export type { DisplayOptions, CellDimensions } from './typstHelpers/shared/types'
 export { generateTypstHelpers } from './typstHelpers/shared/helpers'