fix: simplify skill to single defendToolResult() method, add deps

- Removed separate Tier 1/Tier 2 teaching — skill now presents
  defendToolResult() as the single scan method that does everything
- Added "Do NOT separate them into individual steps" instruction
- Installed @stackone/defender + peer deps in plugin directory so
  the hook script can resolve them from any project
- Added .gitignore for node_modules

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hiskudin

.gitignore

@@ -1 +1,2 @@
 node_modules/
+node_modules/