feat: use QRadioButtons to select z_plan

[fdrgsp]

Use radio button in the z plan widget (as in the grid plan widget)

@tlambert03 what do you think?

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with this PR:

before:

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 94.87179% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.71%. Comparing base (33c1350) to head (3cdeca5). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pymmcore_widgets/useq_widgets/_z.py	94.87%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #385 +/- ## ========================================== - Coverage 90.73% 90.71% -0.03% ========================================== Files 85 85 Lines 9233 9234 +1 ========================================== - Hits 8378 8377 -1 - Misses 855 857 +2 ```

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[tlambert03]

looks great thanks. made some minor visual tweaks. One issue remains though: for some reason, if you click on the words range around and above/below. it works fine. If you click on top/bottom, however, it does switch, but the radio button doesn't switch 🤔

https://github.com/user-attachments/assets/4541441e-d733-4c1b-9396-8d6c09eae1cf

[fdrgsp]

looks great thanks. made some minor visual tweaks. One issue remains though: for some reason, if you click on the words range around and above/below. it works fine. If you click on top/bottom, however, it does switch, but the radio button doesn't switch 🤔

I'll have a look!

[fdrgsp]

looks great thanks. made some minor visual tweaks. One issue remains though: for some reason, if you click on the words range around and above/below. it works fine. If you click on top/bottom, however, it does switch, but the radio button doesn't switch 🤔

I'll have a look!

The issue was that I used the wrong name in the setMode 🤦‍♂️