chore: migrate to chai@6 following established pattern

* explicitly depend on chai and sinon where needed
* wire both together using a globals.js file that is imported
  with the bundle
* workaround tree-shaking so it is not accidentally optimized away

Co-authored-by: nikku <[email protected]>

Author: Copilot

karma.conf.js

@@ -23,7 +23,6 @@ module.exports = function(karma) {
 
     frameworks: [
       'mocha',
-      'sinon-chai',
       'webpack'
     ],
 
@@ -48,6 +47,10 @@ module.exports = function(karma) {
       mode: 'development',
       module: {
         rules: [
+          {
+            test: /test\/globals\.js$/,
+            sideEffects: true
+          },
           {
             test: /\.bpmnlintrc$/,
             use: 'bpmnlint-loader'

test/globals.js

@@ -0,0 +1,7 @@
+import {
+  use
+} from 'chai';
+
+import sinonChai from 'sinon-chai';
+
+use(sinonChai);

test/suite.js

@@ -1,3 +1,5 @@
+import './globals';
+
 var allTests = require.context('.', true, /spec\/.*Spec\.js$/);
 
 allTests.keys().forEach(allTests);