RA, DEC must be double-precision, not single, for radec2pix

[gitosaurus]

Change Description

Ensure that RA and DEC are double-precision before calling radec2pix. When they are single-precision, that function fails with a TypeError.

Closes #458 . Verified during #460 .

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.55%. Comparing base (f99ef80) to head (15144c2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #461   +/-   ##
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  Coverage   94.55%   94.55%           
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  Files          28       28           
  Lines        1615     1615           
=======================================
  Hits         1527     1527           
  Misses         88       88           

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[gitosaurus]

While this fix unblocked the work in #460, it's not quite general enough. Following discussion, will close this in favor of a more abstract fix within the hats project.