Add /list-skills command to show available skills

Shows skill names without descriptions to prevent unnecessary searches.

commands/list-skills.md

@@ -0,0 +1,13 @@
+---
+description: List all available skills by name
+---
+
+Run this command to see what skills exist:
+
+```bash
+find ${CLAUDE_PLUGIN_ROOT}/skills -name "SKILL.md" -type f | sed 's|.*/skills/||; s|/SKILL.md||' | sort
+```
+
+This shows skill paths like `testing/test-driven-development` without loading descriptions.
+
+Use skills-search when you need to find something specific.