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 the separately installed plugin-scanner CLI for package inspection.
+---
+
+# HOL Guard
+
+Use HOL Guard when a workflow needs deterministic security controls around agent or tool execution. HOL Guard is maintained separately at https://github.com/hashgraph-online/hol-guard.
+
+## 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 --version
+```
+
+## Protect a supported agent harness
+
+HOL Guard runtime protection is provided by its own harness integrations. Do not assume this Gemini CLI Security skill itself creates a new interception hook.
+
+Discover the current installation's supported harnesses instead of relying on a static list:
+
+```bash
+hol-guard detect --json
+```
+
+Use an exact supported harness identifier returned by detection. Then install, verify, dry-run, and launch through Guard:
+
+```bash
+hol-guard install <harness>
+hol-guard doctor <harness> --json
+hol-guard run <harness> --dry-run
+hol-guard run <harness>
+```
+
+If detection, install, doctor, or dry-run fails, stop instead of launching the raw harness outside Guard. Treat denied, review-required, and Guard error states as stop conditions.
+
+## Approvals and evidence
+
+Inspect queued decisions and evidence through Guard-owned commands:
+
+```bash
+hol-guard approvals
+hol-guard receipts
+hol-guard status
+```
+
+When the user makes a terminal decision, use the exact request ID shown by `hol-guard approvals`:
+
+```bash
+hol-guard approvals approve <request-id>
+hol-guard approvals deny <request-id>
+```
+
+Never invent an approval or reuse an unrelated request ID.
+
+## Scan plugins, skills, and MCP packages
+
+Package inspection is provided by the separate `plugin-scanner` distribution; installing `hol-guard` does not imply that CLI is present.
+
+If package scanning is needed, install and invoke it separately:
+
+```bash
+pipx install plugin-scanner
+plugin-scanner verify .
+```
+
+Treat high-confidence findings as review blockers until resolved or explicitly accepted. Package scanning is inspection, not runtime enforcement.
+
+## Boundaries
+
+- This skill does not claim that the Gemini CLI Security extension itself adds a HOL Guard pre-tool interception hook.
+- Runtime blocking belongs to HOL Guard's supported harness integrations.
+- `plugin-scanner` is a separate maintainer/CI package and is not a substitute for HOL Guard runtime protection.
+- Never bypass deny, review, or error states by running the protected action directly.