check: report invalid pack names instead of crashing

[mr-raj12]

Fixes #10051.

check() decoded every name in packs/ with hex_to_bin without validating it first. A stray object whose name is not 64 hex digits raised a ValueError that aborted the whole check with a traceback, skipping every pack after it.

Now check() drops names that are not valid pack names, logs each one as an error, and verifies the rest. The check still fails (non-zero exit), so the stray object is not silently ignored.

Also adds a test: it stores one intact pack plus a stray non-hex object and checks that the error is reported and the good pack is still verified.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.77%. Comparing base (800a4b8) to head (da6f388).
⚠️ Report is 7 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10068      +/-   ##
==========================================
+ Coverage   86.76%   86.77%   +0.01%     
==========================================
  Files          98       98              
  Lines       17100    17109       +9     
  Branches     2589     2591       +2     
==========================================
+ Hits        14837    14847      +10     
  Misses       1570     1570              
+ Partials      693      692       -1     

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