test: add unit tests for resolveAgainstBase

[Shreya2005-2005]

Description

Adds unit tests for the resolveAgainstBase function in pkg/unikontainers/utils.go.
This function had no test coverage. The tests cover:

• absolute path returned unchanged
• relative path joined with absolute base
• relative path joined with relative base

Related issues

• Fixes Add more unit tests #96

How was this tested?

Ran the unit tests locally using:
go test ./pkg/unikontainers/... -v -run TestResolveAgainstBase
All 3 test cases passed.

LLM usage

Claude Sonnet 4.6 was used to assist in understanding the codebase and test structure.
All generated code was reviewed and understood before submission.

Checklist

• I have read the contribution guide.
• The linter passes locally (make lint).
• The e2e tests of at least one tool pass locally (make test_ctr, make test_nerdctl, make test_docker, make test_crictl).
• If LLMs were used: I have read the llm policy.

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[cmainas]

Hello @Shreya2005-2005 ,

thank you for submitting this PR. Please read the contribution guide and update your PR.

[Shreya2005-2005]

Hello @Shreya2005-2005 ,

thank you for submitting this PR. Please read the contribution guide and update your PR.

Sure, made the changes according to the PR template could you take a look again