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/triaging-security-incident/SKILL.md

@@ -1,13 +1,10 @@
 ---
 name: triaging-security-incident
-description: 'Performs initial triage of security incidents to determine severity,
-  scope, and required response actions using the NIST SP 800-61r3 and SANS PICERL
-  frameworks. Classifies incidents by type, assigns priority based on business impact,
-  and routes to appropriate response teams. Activates for requests involving incident
-  triage, security alert classification, severity assessment, incident prioritization,
-  or initial incident analysis.
-
-  '
+description: 'Performs initial triage of security incidents using the NIST SP
+  800-61r3 and SANS PICERL frameworks, classifying incident type, assigning priority
+  by business impact, and routing to the appropriate response team. Use when a
+  SIEM/EDR alert needs human classification, concurrent alerts must be prioritized,
+  or a user report or threat-intel IOC match requires initial incident categorization.'
 domain: cybersecurity
 subdomain: incident-response
 tags: