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/deobfuscating-powershell-obfuscated-malware/SKILL.md

@@ -1,8 +1,6 @@
 ---
 name: deobfuscating-powershell-obfuscated-malware
-description: Systematically deobfuscate multi-layer PowerShell malware using AST analysis,
-  dynamic tracing, and tools like PSDecode and PowerDecode to reveal hidden payloads
-  and C2 infrastructure.
+description: Systematically deobfuscates multi-layer PowerShell malware using AST analysis, dynamic tracing, and tools like PSDecode and PowerDecode to reveal hidden payloads and C2 infrastructure. Use during incident response or malware analysis when a PowerShell script is obfuscated with encoding, string manipulation, or invocation tricks and you need to recover the underlying commands, dropped payloads, or C2 endpoints.
 domain: cybersecurity
 subdomain: malware-analysis
 tags: