ci(hrx): bump hrx + add llama-3.1 8b ci coverage

[AaronStGeorge]

llama-3.1 8b is a small model suitable for use in CI.

Summary

This PR:

• Bumps hrx
• Adds llama-3.1 8b as an hrx qualified model
• As llama-3.1 8b is a small model suitable for use in CI, adds CI coverage for hrx

Scope

• This PR addresses one clear issue or change.
• I reviewed the full diff myself before submitting.
• I removed unrelated local changes.
• I kept refactoring separate unless it is required for this change.

Testing

• Code builds without errors locally.
• I tested this change locally.
• I described the testing performed below.

    test/server_llm.py \
    --wrapped-server llamacpp-hrx \
    --backend hrx \
    --cli-binary ./build/lemonade

Documentation

• Documentation is not affected by this change.
• Documentation is affected and has been updated.
• Documentation is affected but will be handled in a separate PR or issue.

Breaking Changes

• This PR introduces breaking changes.
• This PR does not introduce breaking changes.

AI-assisted contribution

Please select one:

• I used AI tools for this PR.
• I did not use AI tools for this PR.

If AI tools were used:

• I verified that I understand the changes.
• I checked for hallucinated APIs, unrelated changes, and incorrect assumptions.