refactor: adopt POSITIONS constants, fix ESLint warnings, break menuUtils into modules

- Replace hardcoded position strings with POSITIONS.* constants
- Prefix unused variables with _ to resolve no-unused-vars warnings
- Fix no-prototype-builtins with Object.prototype.hasOwnProperty.call()
- Extract menuUtils.js (543 lines) into 6 focused modules under menu/
- menuUtils.js now 35 lines, delegates via prototype mixin pattern
- Add 158 unit tests for ConfigManager, MeasurementContainer, ValidationUtils

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/convert/definitions/each.js

@@ -1,5 +1,4 @@
-var metric
-  , imperial;
+var metric;
 
 metric = {
   ea: {

src/convert/definitions/partsPer.js

@@ -1,5 +1,4 @@
-var metric
-  , imperial;
+var metric;
 
 metric = {
   ppm: {

src/convert/index.js

@@ -249,7 +249,7 @@ Converter.prototype.list = function (measure) {
 Converter.prototype.throwUnsupportedUnitError = function (what) {
   var validUnits = [];
 
-  each(measures, function (systems, measure) {
+  each(measures, function (systems, _measure) {
     each(systems, function (units, system) {
       if(system == '_anchors')
         return false;

src/convert/lodash/lodash._basecreate/index.js

@@ -7,7 +7,6 @@
  * Available under MIT license <http://lodash.com/license>
  */
 var isObject = require('./../lodash.isobject'),
-    noop = require('./../lodash.noop'),
     reNative = require('./../lodash._renative');
 
 /* Native method shortcuts for methods with the same name as other `lodash` methods */
@@ -21,7 +20,7 @@ var nativeCreate = reNative.test(nativeCreate = Object.create) && nativeCreate;
  * @param {Object} prototype The object to inherit from.
  * @returns {Object} Returns the new object.
  */
-function baseCreate(prototype, properties) { // eslint-disable-line no-func-assign
+function baseCreate(prototype, _properties) { // eslint-disable-line no-func-assign
   return isObject(prototype) ? nativeCreate(prototype) : {};
 }
 // fallback for browsers without `Object.create`

src/convert/lodash/lodash._createwrapper/index.js

@@ -47,7 +47,7 @@ function createWrapper(func, bitmask, partialArgs, partialRightArgs, thisArg, ar
   var isBind = bitmask & 1,
       isBindKey = bitmask & 2,
       isCurry = bitmask & 4,
-      isCurryBound = bitmask & 8,
+      /* isCurryBound = bitmask & 8, */
       isPartial = bitmask & 16,
       isPartialRight = bitmask & 32;
 

src/convert/lodash/lodash.bind/index.js

@@ -7,7 +7,6 @@
  * Available under MIT license <http://lodash.com/license>
  */
 var createWrapper = require('./../lodash._createwrapper'),
-    reNative = require('./../lodash._renative'),
     slice = require('./../lodash._slice');
 
 /**