Stabilize permissions popup selection tests

[aibrahim-oai]

What is flaky

The permissions popup tests in the TUI are flaky, especially on Windows. They assume the popup opens on a specific row and that a fixed number of Up or Down keypresses will land on a specific preset. They also match popup text too loosely, so a non-selected row can satisfy the assertion.

Why it was flaky

These tests were asserting incidental rendering details rather than the actual selected permission preset. On Windows, the initial selection can differ from non-Windows runs. Some tests also searched the entire popup for text like Guardian Approvals or (current), which can match a row that is visible but not selected. Once the popup order or current preset shifted slightly, a test could fail even though the UI behavior was still correct.

How this PR fixes it

This PR adds helpers that identify the selected popup row and selected preset name directly. The tests now assert the current selection by name, navigate to concrete target presets instead of assuming a fixed number of keypresses, and explicitly set the reviewer state in the cases that require Guardian Approvals to be current.

Why this fix fixes the flakiness

The assertions now track semantic state, not fragile text placement. Navigation is target-based instead of order-based, so Windows/non-Windows row differences and harmless popup layout changes no longer break the tests. That removes the scheduler- and platform-sensitive assumptions that made the popup suite intermittent.