Improve focus-trap behavior of modal container

[IsaSih]

Setup

• Rancher version:

Rancher v2.14.0
Dashboard v2.14.0

Describe the bug
Found while fixing rancher/qa-tasks#2270

There's a workaround in place to test downloading the diagnostics package JSON. We're using cy.on('uncaught:exception') to ignore known failures due to AppModal.vue that always activates a focus-trap on modal-container-element, but in this e2e test diagnostic.spec.ts, the modal is being closed so quickly (right after clicking “download”) that the trap is still activating while the container has no tabbable elements. When focus-trap activates and can’t find any tabbable node inside its container, it throws:

“Your focus-trap must have at least one container with at least one tabbable node in it at all times.”

To Reproduce

Run diagnostic.spec.ts in CI.

Result
AppModal.vue is wiring the trap by watching a variable and then calling createFocusTrap(...).activate() on #modal-container-element, resulting in the test failure.

Expected Result
The modal container must be programmatically focusable and provide a fallbackFocus for focus-trap, so this error does not fire when tabbable controls are temporarily unavailable.

[github-actions]

🤖 Issue grooming analysis

✅ Clear Problem Statement — The title accurately summarizes the bug. The body explains that AppModal.vue activates a focus-trap on #modal-container-element, and when the modal closes before tabbable elements are available, focus-trap throws an error. The context is clearly tied to diagnostic.spec.ts in CI.

✅ Acceptance Criteria — The Expected Result is concrete and verifiable: the modal container must be programmatically focusable and provide a fallbackFocus for focus-trap, preventing the error when tabbable controls are temporarily unavailable.

✅ Technical Details — Specific files identified (AppModal.vue, diagnostic.spec.ts), the exact error message is provided ("Your focus-trap must have at least one container with at least one tabbable node in it at all times."), and a related issue is linked (rancher/qa-tasks#2270).

✅ Reproducibility — Steps to reproduce are clear: run diagnostic.spec.ts in CI. Actual and expected results are both stated.

This analysis was generated automatically based on the repository's grooming checklist.

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