[bennibyx]

Title: Fix annotated tag commit SHA resolution

Description:

Summary

• Resolve annotated Git tags to their underlying Git objects.
• Follow nested annotated tags until the target object is reached.
• Use the SHA only when the resolved object is a commit.

Testing

• dotnet build src/PinAction/PinAction.csproj succeeds.
• git diff --check passes.

Automated or targeted tests for annotated tags have not yet been run.