Add ISO internal audit evidence gates

[cuph7022]

Summary

• Add the evidence gate requested by [REVIEW] iso27001-gap: add internal-audit sampling and impartiality evidence gates #1633.
• Add a focused output table so assessments capture the required proof consistently.
• Add a pitfall warning for the main false-positive or false-negative risk.

Closes #1633

Validation

• Reviewed generated Markdown changes through the GitHub API.
• Confirmed the patch is scoped only to $(System.Collections.Hashtable.Path).
• Did not clone the repository, install dependencies, or run project code.