chore: Migrate golden-layout tests from Karma to Jest (deephaven#2611)

Migrate golden-layout tests from Karma/Jasmine to Jest/TypeScript using
AI and a planning doc. Migration worked, I manually spot checked a bunch
of them for sanity and they seemed like it made wise choices, and even
uncovered a bug.

- Migrate all 21 test files from /test/.js to /src/tests/.test.ts
- Tests kept with same name, and same coverage
- Remove Karma configuration and legacy test files
- Enable previously skipped drag tests with jQuery mocks
- Fix bug in replaceChild that caused destruction errors


Changes

Test Migration

- Convert Jasmine syntax to Jest (spyOn → jest.spyOn, waitsFor/runs →
async/await)
- Add shared test utilities in src/test-utils/testUtils.ts
- Remove Karma devDependencies (babelify, browserify, karma-browserify,
watchify)
- Enabled Drag Tests
- Test count decreased, as cleanup is afterEach rather than deticated in
each test

The drag tests were skipped because jsdom doesn't support jQuery
dimension methods. Added mocks for $.fn.offset, $.fn.width, $.fn.height,
$.fn.outerWidth, $.fn.outerHeight, and
$.fn.is(':visible').

Bug Fix: replaceChild Event Listener Leak

When replaceChild() swapped a tab's content item, it directly assigned
the new reference without transferring event listeners. This caused "No
subscriptions to unsubscribe for event destroy" errors when destroying
the layout after drag-drop split operations.

Fix: Added Tab.setContentItem() method that properly transfers destroy
and titleChanged
listeners from the old content item to the new one.

Test Results

21 tests migrated, all passing.

Test Plan

- Manually spot check tests to compare coverage
- All golden-layout tests pass
- TypeScript compiles without errors

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>
Co-authored-by: mofojed <4505624+mofojed@users.noreply.github.com>

Author: 4 people

.github/workflows/unit.yml

@@ -78,14 +78,12 @@ jobs:
         run: |
           npm run test:unit -- --cacheDirectory $PWD/.jest-cache
           npm run test:lint -- --changedSince origin/${{ github.event.pull_request.base.ref }} --cacheDirectory $PWD/.jest-cache
-          npm run test:golden-layout
 
       - name: Unit Test (Push)
         if: ${{ github.event_name == 'push' }}
         run: |
           npm run test:unit -- --cacheDirectory $PWD/.jest-cache
           npm run test:lint -- --lastCommit --cacheDirectory $PWD/.jest-cache
-          npm run test:golden-layout
 
       - name: Codecov report
         uses: codecov/codecov-action@v4