[MagnusG2]

What github issue is this PR for, if any?

Related to #6833

What changed, and why?

• Added Jest coverage for the two-minute session timeout warning.
• Added coverage for reloading after the full session timeout has elapsed.
• Replaced the negative warning threshold used by the previous test with a realistic three-minute timeout.
• Used Jest fake timers and a Node test environment so window.location.reload can be mocked without jsdom navigation errors.

No production code was changed.

How is this tested?

• npm run test -- app/javascript/__tests__/two_minute_warning_session_timeout.test.js
  • 3 tests passed.
• npm run lint -- app/javascript/__tests__/two_minute_warning_session_timeout.test.js
• npm run test
  • 15 test suites passed.
  • 126 tests passed.

Screenshots please :)

Not applicable — this is a test-only change with no UI changes.