fix: "p" at the front of axis order when auto-inserting current stage position

[boydcpeters]

Ensure "p" axis is first when auto-inserting current position

When no stage positions are provided, the current position is added automatically and the "p" axis is placed at the front of axis_order.

Closes #550

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.42%. Comparing base (8c8f76e) to head (bcbdad5).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #555      +/-   ##
==========================================
- Coverage   87.42%   87.42%   -0.01%     
==========================================
  Files         115      115              
  Lines       14081    14079       -2     
==========================================
- Hits        12310    12308       -2     
  Misses       1771     1771              

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[tlambert03]

we can't think of any critical reason against this. I think the assumption was just to follow the more likely multi-position pattern, where usually people want to visit each position per time point (as opposed to do the full t at p0 before moving to p1). But of course, that distinction is moot anyway when there's a single position. So it really doesn't matter, and consistency seems better here. thanks @boydcpeters

[boydcpeters]

Ahh that makes sense, I can see how this came about when imaging multiple positions, where visiting each position for each timepoint is the more common pattern. Thanks for the clarification!