test: add unit tests for AIWidget

[kh-ub-ayb]

Summary

This PR adds a new unit test suite targeting the AIWidget to test the constructor, initialization steps, and helper methods.

Changes

• Added 13 new unit tests in js/widgets/tests/aiwidget.test.js
• No changes to source code

Test Coverage

Describe Block	Tests	Coverage
Constructor and Properties	1	Ensures basic properties (sample configuration, centers, tracking objects) initialize correctly without throwing.
State Modifiers	3	Tests behavior of _usePitch, _useAccidental, and _useOctave properly updating internal pointer variables.
Init Method	1	Verifies that widget window instantiates correctly, creates buttons, and sets up analysis listeners on load.
Methods and Helpers	8	Extensively tests pure and interdependent methods required for AI audio sampling: threshold checking (getSampleLength), adding custom tracks (_addSample), connecting references to Tone.Analyser (reconnectSynthsToAnalyser), and triggering/stopping playback variables (_playSample, pause, resume).

Scope

• Only js/widgets/tests/aiwidget.test.js was added.

Verification

• All 13 tests pass

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.

[kh-ub-ayb]

@walterbender @omsuneri please review