package list: show "push" button when no packages

[nl0]

TODO

• wordsmith if necessary @akarve

[codecov-io]

Codecov Report

Merging #1843 into master will decrease coverage by 0.75%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1843      +/-   ##
==========================================
- Coverage   89.48%   88.73%   -0.76%     
==========================================
  Files          62       93      +31     
  Lines        7237    11767    +4530     
==========================================
+ Hits         6476    10441    +3965     
- Misses        761     1326     +565     

Flag	Coverage Δ
#api-python	87.70% <ø> (-0.18%)	⬇️
#lambda	92.29% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
api/python/quilt3/util.py	80.42% <0.00%> (-1.43%)	⬇️
api/python/tests/test_data_transfer.py	99.02% <0.00%> (-0.98%)	⬇️
api/python/quilt3/data_transfer.py	77.77% <0.00%> (-0.17%)	⬇️
...ircleci/project/api/python/quilt3/backends/base.py	89.20% <0.00%> (ø)
...sers/circleci/project/api/python/tests/conftest.py	92.68% <0.00%> (ø)
.../circleci/project/api/python/tests/test_formats.py	100.00% <0.00%> (ø)
...:/Users/circleci/project/api/python/quilt3/main.py	55.85% <0.00%> (ø)
...ers/circleci/project/api/python/quilt3/packages.py	91.85% <0.00%> (ø)
...ers/circleci/project/api/python/tests/test_util.py	100.00% <0.00%> (ø)
...ers/circleci/project/api/python/quilt3/registry.py	0.00% <0.00%> (ø)
... and 24 more

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[akarve]

Good start; we should merge but also backlog: if the user clicks Push Package, uses DND, and pushes, but then doesn't "browse" the package and closes window, then I think the list behind remains empty? Not sure if/how we can fix this but it might be a confusing UX.