"Update tests" does not sync new test cases when editing a Test Run (out of sync with test plan)

[Rustam-Nych]

Describe the bug
When editing an existing Test Run, if the linked test plan has new test cases added, the "Update tests" button (triggered via the "There are out of sync with the test plan" warning) does not pull in the new tests. The test count in the run remains outdated.

To Reproduce

1. Create a Test Run linked to a test plan (e.g. "Release | Estuary")
2. Add new test cases to the linked test plan after the run is created
3. Open the Test Run for editing — notice the warning: "There are out of sync with the test plan"
4. Click "Update tests"
5. See that the test count in the run does NOT update — new test cases are not added

Expected behavior
Clicking "Update tests" should sync the Test Run with the current state of the linked test plan, pulling in all newly added test cases and updating the total test count accordingly.

Screenshots

Desktop (please complete the following information):

• OS: Version 26.3.1 (25D2128)
• Browser: Chrome
• Browser Version: 147.0.7727.117
• Application: production