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/exploiting-broken-link-hijacking/SKILL.md

@@ -1,8 +1,12 @@
 ---
 name: exploiting-broken-link-hijacking
-description: Discover and exploit broken link hijacking vulnerabilities by identifying
-  references to expired domains, decommissioned cloud resources, and dead external
-  services that can be claimed by an attacker.
+description: >-
+  Discovers and exploits broken link hijacking by spidering a site (Burp Suite
+  Spider, Scrapy, curl scraping), extracting referenced external scripts/domains,
+  and checking DNS/CNAME records and domain registration status for expired or
+  unclaimed resources an attacker could register. Use for subdomain takeover
+  testing, supply-chain review of third-party scripts, or bug bounty hunting for
+  hijackable external resources.
 domain: cybersecurity
 subdomain: web-application-security
 tags: