docs: fix agent config sample links

[Ricky-7-Yan]

Link to Issue or Description of Change

Problem:

The two links under "Related samples" in the Agent Config guide only traverse three directories upward. From docs/guides/agents/config/, that resolves under the nonexistent docs/contributing/ directory, so both links are broken.

Solution:

Traverse one additional directory upward so the links resolve to the repository-level contributing/samples/ examples.

Testing Plan

Documentation-only link correction:

• resolved both updated relative paths from the guide's directory and confirmed both target README.md files exist
• ran git diff --check successfully
• uvx mdformat --check reports that the existing file is not formatted under bare mdformat defaults; I did not reformat the whole document because that would introduce unrelated changes

Checklist

• I have read CONTRIBUTING.md
• I reviewed the two-line diff and verified both targets
• Tests are not applicable to this small documentation fix
• No dependent changes are required

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