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/performing-threat-intelligence-sharing-with-misp/SKILL.md

@@ -1,8 +1,12 @@
 ---
 name: performing-threat-intelligence-sharing-with-misp
-description: Use PyMISP to create, enrich, and share threat intelligence events on
-  a MISP platform, including IOC management, feed integration, STIX export, and community
-  sharing workflows.
+description: >-
+  Uses PyMISP (the official MISP REST API library) to create events with
+  structured IOCs (IPs, domains, hashes, URLs), enrich them with MITRE ATT&CK
+  tags and galaxy clusters, manage sharing groups and distribution levels,
+  search existing intelligence, and export in STIX 2.1 format. Use when
+  creating, enriching, or sharing threat intelligence events on a MISP
+  instance, or integrating IOC feeds with other platforms.
 domain: cybersecurity
 subdomain: threat-intelligence
 tags: