[Fix] Apply Time Conductor mode changes on submit

[LarryHu0217]

Closes #8258

Describe your changes:

• Keep global Time Conductor mode selections local to the open popup.
• Commit the pending mode only when the user submits the fixed bounds or realtime offsets.
• Leave the active mode and URL unchanged when the popup is discarded.
• Update the shared e2e mode helper and add regression coverage for discarding pending Fixed-to-Real-Time and Real-Time-to-Fixed changes.

Validation

• Time Conductor e2e spec: 8 passed, 4 existing fixme tests skipped.
• Unit suite: 975 passed, 67 skipped.
• Production build and TypeScript compilation passed.
• ESLint, Prettier check, CSpell, and git diff --check passed for the changed files.

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Is this a notable change that will require a special callout in the release notes? No, this restores the existing discard behavior for a popup setting.

Author Checklist

• Changes address original issue?
• Tests included and/or updated with changes?
• Has this been smoke tested?
• Have you associated this PR with a type: label? I do not have permission to add labels.
• Have you associated a milestone with this PR? Leaving this for maintainers.
• Testing instructions included in associated issue OR is this a dependency/testcase change?

Reviewer Checklist

• Changes appear to address issue?
• Reviewer has tested changes by following the provided instructions?
• Changes appear not to be breaking changes?
• Appropriate automated tests included?
• Code style and in-line documentation are appropriate?