feat: add HOL Guard security skill

[kantorcodes]

Summary

Adds a hol-guard Agent Skill to the official Oz Skills catalog.

The skill teaches Warp/Oz agents to install and invoke HOL Guard directly for supported local AI harness protection, approval/evidence review, and plugin/skill/MCP package verification. It keeps the runtime boundary accurate: Warp/Oz can operate HOL Guard through this skill, but the skill does not claim Warp itself is a protected HOL Guard harness.

The workflow is adapted from the canonical HOL Guard Agent Skill: https://github.com/hashgraph-online/hol-guard-plugin/blob/main/skills/hol-guard/SKILL.md

Validation

• Path and frontmatter follow this repository's AGENTS.md conventions.
• name matches the hol-guard directory.
• Description follows the required imperative sentence + Use when... pattern.
• Commands use the current HOL Guard runtime/scanner split and supported harness names from the canonical skill.
• Interactive Warp-agent testing was not available in this execution environment, so it is not claimed as completed.