chore: package sanitation — prune dead code, tighten internal types

Dead code removed:
- 11 unused tracking wrapper functions in `lib/analytics/index.ts`
  (trackToolEngaged, trackToolSessionSummary, trackPageScrollDepth,
  trackLearnPanelScrollDepth, trackOutboundClick,
  trackMobileControlsToggle, trackFileUploadError, trackJsError,
  trackWebGLError, trackCapabilityCheck) plus `getGlobalProperties`.
  Consumers can call `dispatch()` directly when needed; the wrappers
  added zero behaviour and rotted into "exported but never imported"
  cruft. Their type imports are pruned too.
- `OverlayRect` type and `overlayRects` mutable export from the
  megapixels-size-visualizer drawOverlay — leftover hit-test scratch
  buffer from a sensor-size-comparison copy/paste; never read.
- Legacy `ToolEducation` / `Challenge` / `ChallengeOption` / `ProTip`
  types in `lib/data/education/types.ts` — pre-i18n schema kept after
  the skeleton refactor took over; nothing consumes them.
- `DOF_SCENE_PRESETS` "backward-compat alias for existing DoF
  Calculator component (until Task 8 renames it)" — Task 8 happened
  long ago. The only consumer was its own test file.
- `ALL_MP_IDS` / `ALL_SENSOR_IDS` intermediate arrays — only the
  `_SET` variants were ever read; inlined the source.
- Duplicate local `formatDist` helpers in HyperfocalMiniTable and
  HyperfocalBadge — both reimplemented the dof-diagram-helpers
  version (minus the `isFinite` infinity guard). Now import the
  shared one, gaining the ∞ formatting for free.

API surface tightened (removed `export` from internal-only types):
- `FramingPreset`, `GlossaryEntry`, `FaqSkeleton`, `ToolFaqs`,
  `WbPreset`, `WbScene`, `ExposureScene`, `PrintSizePreset`,
  `SceneObject`, `SceneDef`, `ScenePickerScene`, `MagnifierState`,
  `SceneAssets`, `PillBounds`, `GeoArrays`, `BokehCircle`,
  `MIN_DIST`, `MAX_DIST`. Each was only referenced inside its own
  module; making them file-local stops them from looking like a
  public contract.

Bug hardening:
- `loadCustomSensors` now validates that the parsed JSON is an array
  before iterating. Previously a corrupted/non-array localStorage
  value would partially mutate `COMMON_MP` before throwing into the
  catch — unlikely in practice but messy.

Verified: 868 unit tests, 122 chromium smoke specs, type-check, lint,
and production build (720 static pages) all pass.

Author: kevinkiklee

src/app/[locale]/color-scheme-generator/_components/useMagnifier.ts

@@ -2,7 +2,7 @@
 
 import { useState, useRef, useCallback } from 'react'
 
-export interface MagnifierState {
+interface MagnifierState {
   vpX: number
   vpY: number
   hex: string

src/app/[locale]/exposure-simulator/_components/useExposureRenderer.ts

@@ -11,7 +11,7 @@ import {
 } from './webglHelpers'
 import { runRenderPipeline, cleanupResources } from './renderPipeline'
 
-export interface SceneAssets {
+interface SceneAssets {
   photo: string
   depthMap: string
   motionMask: string

src/app/[locale]/fov-simulator/_components/canvasTypes.ts

@@ -1,6 +1,6 @@
 import type { LensConfig } from '@/lib/types'
 
-export interface PillBounds {
+interface PillBounds {
   x: number
   y: number
   w: number

src/app/[locale]/hyperfocal-simulator/_components/HyperfocalBadge.tsx

@@ -1,17 +1,13 @@
 'use client'
 
 import { useTranslations } from 'next-intl'
+import { formatDist } from '@/components/shared/dof-diagram-helpers'
 
 interface HyperfocalBadgeProps {
   isAtHyperfocal: boolean
   nearLimit: number
 }
 
-function formatDist(m: number): string {
-  if (m < 1) return `${(m * 100).toFixed(0)} cm`
-  return `${m.toFixed(2)} m`
-}
-
 export function HyperfocalBadge({ isAtHyperfocal, nearLimit }: HyperfocalBadgeProps) {
   const t = useTranslations('toolUI.hyperfocal-simulator')
   if (!isAtHyperfocal) return null

src/app/[locale]/hyperfocal-simulator/_components/HyperfocalMiniTable.tsx

@@ -3,18 +3,14 @@
 import { useTranslations } from 'next-intl'
 import { calcHyperfocal } from '@/lib/math/dof'
 import { APERTURES } from '@/lib/data/camera'
+import { formatDist } from '@/components/shared/dof-diagram-helpers'
 
 interface HyperfocalMiniTableProps {
   focalLength: number
   aperture: number
   coc: number
 }
 
-function formatDist(m: number): string {
-  if (m < 1) return `${(m * 100).toFixed(0)} cm`
-  return `${m.toFixed(2)} m`
-}
-
 export function HyperfocalMiniTable({ focalLength, aperture, coc }: HyperfocalMiniTableProps) {
   const t = useTranslations('toolUI.hyperfocal-simulator')
   return (

src/app/[locale]/megapixels-size-visualizer/_components/drawOverlay.ts

@@ -3,9 +3,6 @@ import { mpToPixelDimensions } from '@/lib/math/resolution'
 import { printSizeMm } from '@/lib/math/megapixel'
 import { drawRect, rgba, roundRect } from './drawHelpers'
 
-export type OverlayRect = { id: string; x: number; y: number; w: number; h: number }
-export let overlayRects: OverlayRect[] = []
-
 export function drawOverlay(
   ctx: CanvasRenderingContext2D,
   canvasWidth: number,
@@ -17,7 +14,6 @@ export function drawOverlay(
   _units: UnitSystem,
   hoveredId: string | null,
 ): { contentHeight: number; pxPerMm: number } {
-  overlayRects = []
   if (visibleMps.length === 0) {
     return { contentHeight: 300, pxPerMm: 0 }
   }
@@ -64,8 +60,6 @@ export function drawOverlay(
 
     const alpha = hoveredId && hoveredId !== mp.id ? 0.3 : 1
     drawRect(ctx, x, y, w, h, mp.color, alpha)
-
-    overlayRects.push({ id: mp.id, x, y, w, h })
   }
 
   // Labels: pills in a column to the left of the largest rectangle, with leader lines

src/app/[locale]/megapixels-size-visualizer/_components/megapixelTypes.ts

@@ -38,4 +38,3 @@ export type PrintTableControlsProps = {
   onBitDepthChange: (b: BitDepth) => void
 }
 
-export { type UnitSystem, type CustomMegapixel, type ViewingDistance, type BitDepth }

src/app/[locale]/perspective-compression-simulator/_components/compressionGeometry.ts

@@ -1,6 +1,6 @@
 import { GROUND_COLOR, GRID_COLOR } from './compressionConstants'
 
-export interface GeoArrays {
+interface GeoArrays {
   positions: number[]
   normals: number[]
   colors: number[]

src/app/[locale]/sensor-size-comparison/_components/sensorSizeHelpers.ts

@@ -6,8 +6,7 @@ import type { StoredCustomSensor } from './sensorSizeTypes'
 export let customColorIdx = 0
 export function setCustomColorIdx(n: number) { customColorIdx = n }
 
-export const ALL_SENSOR_IDS = SENSORS.map((s) => s.id)
-export const ALL_SENSOR_ID_SET = new Set(ALL_SENSOR_IDS)
+export const ALL_SENSOR_ID_SET = new Set(SENSORS.map((s) => s.id))
 
 export function rgba(hex: string, a: number): string {
   const n = parseInt(hex.replace('#', ''), 16)
@@ -64,7 +63,9 @@ export function loadCustomSensors(): Required<SensorPreset>[] {
   try {
     const raw = localStorage.getItem(STORAGE_KEY)
     if (!raw) return []
-    const stored: StoredCustomSensor[] = JSON.parse(raw)
+    const parsed = JSON.parse(raw)
+    if (!Array.isArray(parsed)) return []
+    const stored = parsed as StoredCustomSensor[]
     for (const s of stored) {
       if (s.mp && s.mp > 0) {
         COMMON_MP[s.id] = [{ mp: s.mp, models: s.name }]

src/components/shared/ScenePicker.tsx

@@ -5,7 +5,7 @@ import { useTranslations } from 'next-intl'
 import { trackToolInteraction } from '@/lib/analytics'
 import styles from './ScenePicker.module.css'
 
-export interface ScenePickerScene {
+interface ScenePickerScene {
   id: string
   name: string
   src: string