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-jwt-algorithm-confusion-attack/SKILL.md

@@ -1,14 +1,11 @@
 ---
 name: exploiting-jwt-algorithm-confusion-attack
-description: 'Exploits JWT algorithm confusion vulnerabilities where the server''s
-  token verification library accepts the algorithm specified in the JWT header rather
-  than enforcing a fixed algorithm. The tester manipulates the alg header to switch
-  from RS256 to HS256 (using the RSA public key as the HMAC secret), sets alg to none
-  to bypass signature verification, or exploits kid/jku/x5u header injection to supply
-  attacker-controlled keys. Activates for requests involving JWT algorithm confusion,
-  alg none attack, key confusion attack, or JWT signature bypass.
-
-  '
+description: >-
+  Exploits JWT algorithm confusion where the server's verification library trusts
+  the alg named in the token header, by switching RS256 to HS256 (signing with the
+  RSA public key as HMAC secret), setting alg to none, or injecting kid/jku/x5u
+  headers to supply an attacker-controlled key. Use when testing RS256 JWT auth
+  for algorithm downgrade, alg:none bypass, or key-confusion signature forgery.
 domain: cybersecurity
 subdomain: api-security
 tags: