rf(EnsureRemoteName): satisfy type-annotation checker

[mih]

There should be no functional change, just assert statements in strategic places that help mypy infer that things are correct the way they are.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.40%. Comparing base (c77087b) to head (41e12a6). Report is 99 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #718 +/- ## ========================================== - Coverage 92.43% 92.40% -0.03% ========================================== Files 193 193 Lines 14135 14120 -15 Branches 2134 2134 ========================================== - Hits 13065 13048 -17 - Misses 806 808 +2 Partials 264 264 ```

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