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-rate-limiting-and-throttling/SKILL.md

@@ -1,14 +1,11 @@
 ---
 name: implementing-api-rate-limiting-and-throttling
-description: 'Implements API rate limiting and throttling controls using token bucket,
-  sliding window, and fixed window algorithms to protect against brute force attacks,
-  credential stuffing, resource exhaustion, and API abuse. The engineer configures
-  per-user, per-IP, and per-endpoint rate limits using Redis-backed counters, API
-  gateway plugins, or application middleware, and implements proper HTTP 429 responses
-  with Retry-After headers. Activates for requests involving rate limiting implementation,
-  API throttling setup, request quota management, or API abuse prevention.
-
-  '
+description: 'Implements API rate limiting and throttling with token bucket, sliding
+  window, and fixed window algorithms, configuring per-user, per-IP, and per-endpoint
+  limits via Redis-backed counters, API gateway plugins, or middleware, and returning
+  proper HTTP 429 responses with Retry-After headers. Use when setting up request
+  quota management or preventing brute force, credential stuffing, and resource exhaustion
+  attacks against APIs.'
 domain: cybersecurity
 subdomain: api-security
 tags: