Rewrite 548 skill descriptions to the activation rubric

Each rewritten description now states both what the skill does (concrete
capability, named tools/artifacts) and an explicit when-to-use trigger,
improving agent discovery/activation. Grounded in each skill's own body;
changes confined to the `description` field only (bodies and all other
frontmatter untouched). Produced by a gated audit->rewrite->recheck loop
(548 -> 0 flagged) with a sampled anti-invention check (0 ungrounded).

Schema: 817/817 pass. Framework-ID gate: 0 defects.

skills/securing-agentic-ai-tool-invocation/SKILL.md

@@ -1,6 +1,11 @@
 ---
 name: securing-agentic-ai-tool-invocation
-description: Apply least-privilege tool allowlisting, identity binding, and human-in-the-loop controls for agent tool calls.
+description: Implements defense-in-depth controls at an AI agent's tool-invocation
+  boundary using tool allowlisting, least-privilege identity binding, NeMo Guardrails
+  policy enforcement, human-in-the-loop approval, and audit logging. Use when hardening
+  an agent that calls tools with real side effects (email, payments, file writes,
+  code execution), mapping OWASP Agentic AI Top 10 controls, or bounding prompt-injection
+  blast radius.
 domain: cybersecurity
 subdomain: ai-security
 tags: