Fix push into OCI with tag

[jonesbusy]

Description

Fix push into OCI with tag

Found during interactive tests.

Testing done

Added a new automated test

Submitter checklist

• I have read and understood the CONTRIBUTING guide
• I have run mvn license:update-file-header, mvn spotless:apply, pre-commit run -a, mvn clean install before opening the PR

[codecov]

Codecov Report

Attention: Patch coverage is 76.74419% with 10 lines in your changes missing coverage. Please review.

Project coverage is 84.99%. Comparing base (4943281) to head (08caeae).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/main/java/land/oras/OCILayout.java	73.91%	2 Missing and 4 partials ⚠️
src/main/java/land/oras/Registry.java	71.42%	2 Missing ⚠️
src/main/java/land/oras/utils/JsonUtils.java	33.33%	2 Missing ⚠️

❌ Your patch status has failed because the patch coverage (76.74%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #210      +/-   ##
============================================
- Coverage     85.14%   84.99%   -0.15%     
- Complexity      429      439      +10     
============================================
  Files            33       33              
  Lines          1447     1473      +26     
  Branches        164      174      +10     
============================================
+ Hits           1232     1252      +20     
- Misses          143      146       +3     
- Partials         72       75       +3     

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