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/implementing-api-abuse-detection-with-rate-limiting/SKILL.md

@@ -1,8 +1,10 @@
 ---
 name: implementing-api-abuse-detection-with-rate-limiting
-description: Implement API abuse detection using token bucket, sliding window, and
-  adaptive rate limiting algorithms to prevent DDoS, brute force, and credential stuffing
-  attacks.
+description: Implements API abuse detection using token bucket, sliding window, and
+  fixed window rate-limiting algorithms backed by Redis, including adaptive limits
+  that tighten during detected attacks and relax during normal traffic. Use when
+  defending APIs against DDoS, brute force login attempts, credential stuffing, or
+  scraping abuse and you need to design or tune rate-limiting logic.
 domain: cybersecurity
 subdomain: api-security
 tags: