feat(skills): add HOL Guard security skill

skills/hol-guard/SKILL.md

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+---
+name: hol-guard
+description: Use the third-party HOL Guard CLI for supported-harness protection, approvals and evidence, and security scanning of agent plugins, skills, and MCP packages.
+---
+
+# HOL Guard
+
+Use HOL Guard when a workflow needs deterministic security controls around agent or tool execution, or when reviewing an agent plugin, skill, or MCP package.
+
+HOL Guard is maintained separately at https://github.com/hashgraph-online/hol-guard-plugin.
+
+## Install
+
+Prefer an isolated CLI install:
+
+```bash
+pipx install hol-guard
+```
+
+If `pipx` is unavailable:
+
+```bash
+python -m pip install --user hol-guard
+```
+
+Check the installed CLI before using it:
+
+```bash
+hol-guard --help
+```
+
+## Protect a supported agent harness
+
+HOL Guard runtime protection is provided by its own harness integrations. Do not assume Gemini CLI itself is a supported interception target.
+
+Check the currently installed CLI for supported harness commands:
+
+```bash
+hol-guard install --help
+hol-guard run --help
+```
+
+For a harness HOL Guard currently supports:
+
+```bash
+hol-guard install <harness>
+hol-guard doctor
+hol-guard run <harness>
+```
+
+Treat denied, review-required, and Guard error states as stop conditions. Do not execute the protected downstream action outside the Guard-owned flow to bypass a decision.
+
+## Approvals and evidence
+
+Use the installed CLI help for the current approval, receipt, and evidence commands before acting:
+
+```bash
+hol-guard --help
+```
+
+Keep the policy decision and attempted action together in the evidence trail so a reviewer can distinguish allowed, denied, and review-required executions.
+
+## Scan plugins, skills, and MCP packages
+
+HOL Guard also provides package-scanning capabilities for suspicious agent extensions. Check the installed scanner interface first:
+
+```bash
+plugin-scanner --help
+```
+
+Scan the local package or repository using the current syntax shown by `plugin-scanner --help`. Treat high-confidence findings as review blockers until resolved or explicitly accepted.
+
+## Boundaries
+
+- This skill does not claim that Gemini CLI exposes a native HOL Guard pre-tool hook.
+- Runtime blocking belongs to HOL Guard's supported harness integrations.
+- Package scanning is inspection; it is not a substitute for runtime enforcement.
+- Never bypass deny, review, or error states by running the protected action directly.