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/detecting-stuxnet-style-attacks/SKILL.md

@@ -1,11 +1,11 @@
 ---
 name: detecting-stuxnet-style-attacks
-description: 'This skill covers detecting sophisticated cyber-physical attacks that
-  follow the Stuxnet attack pattern of modifying PLC logic while spoofing sensor readings
-  to hide the manipulation from operators. It addresses PLC logic integrity monitoring,
-  physics-based process anomaly detection, engineering workstation compromise indicators,
-  USB-borne attack vectors, and multi-stage attack chain detection spanning IT-to-OT
-  lateral movement through to process manipulation.
+description: 'Detects sophisticated cyber-physical attacks that follow the Stuxnet
+  pattern of modifying PLC logic while spoofing sensor readings to hide the
+  manipulation, using PLC logic integrity monitoring (Claroty xDome, Nozomi
+  Guardian) and physics-based process anomaly detection. Use when hunting for
+  IT-to-OT lateral movement or discrepancies between PLC program state and
+  physical process behavior in ICS/SCADA environments.
 
   '
 domain: cybersecurity