chore: migrate to chai@6

[Copilot]

Migrates from chai@4 to chai@6, following the pattern established in bpmn-js-token-simulation#176.

Changes

• Created test/globals.js to wire chai and sinon-chai together via chai's use() function
• Imported globals module in test entry point to ensure setup runs before tests
• Removed sinon-chai from karma frameworks (now handled via explicit wiring)
• Added webpack sideEffects rule for globals module to prevent tree-shaking
• Added explicit import { expect } from 'chai' in all test files that use chai assertions

// test/globals.js
import { use } from 'chai';
import sinonChai from 'sinon-chai';

use(sinonChai);

This explicit wiring and importing approach is required because chai@6 no longer auto-registers plugins globally in bundled environments.

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[Copilot]

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[nikku]

@copilot Please ensure we explicitly import chai and sinon where previously used as a global, i.e. add import { expect } from 'chai' in every file that consumes expect

[Copilot]

@copilot Please ensure we explicitly import chai and sinon where previously used as a global, i.e. add import { expect } from 'chai' in every file that consumes expect

Done! Added explicit import { expect } from 'chai'; to both test files that use expect (7b01c3c):

• test/spec/LintingSpec.js
• test/distro/distroSpec.js

[nikku]

Incorporated into #76