feat(llm-security-copilot): port llm-security v5.1.0 to GitHub Copilot CLI

Full port of llm-security plugin for internal use on Windows with GitHub
Copilot CLI. Protocol translation layer (copilot-hook-runner.mjs)
normalizes Copilot camelCase I/O to Claude Code snake_case format — all
original hook scripts run unmodified.

- 8 hooks with protocol translation (stdin/stdout/exit code)
- 18 SKILL.md skills (Agent Skills Open Standard)
- 6 .agent.md agent definitions
- 20 scanners + 14 scanner lib modules (unchanged)
- 14 knowledge files (unchanged)
- 39 test files including copilot-port-verify.mjs (17 tests)
- Windows-ready: node:path, os.tmpdir(), process.execPath, no bash

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/llm-security-copilot/tests/fixtures/posture-scan/grade-a-project/agents/scanner-agent.md

@@ -0,0 +1,10 @@
+---
+name: scanner-agent
+description: Scans files for security issues
+model: sonnet
+tools: ["Read", "Glob", "Grep"]
+---
+
+# Scanner Agent
+
+Read-only agent that scans project files.