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/performing-content-security-policy-bypass/SKILL.md

@@ -1,8 +1,11 @@
 ---
 name: performing-content-security-policy-bypass
-description: Analyze and bypass Content Security Policy implementations to achieve
-  cross-site scripting by exploiting misconfigurations, JSONP endpoints, unsafe directives,
-  and policy injection techniques.
+description: Analyze Content-Security-Policy headers and bypass them to achieve cross-site
+  scripting by exploiting unsafe-inline/unsafe-eval, whitelisted JSONP endpoints, base-uri
+  and form-action gaps, and nonce/hash weaknesses, then exfiltrate data even without
+  script-src control. Use during web application security assessments or bug bounty
+  hunting when XSS is found but blocked by CSP, or when auditing CSP header configuration
+  for weaknesses.
 domain: cybersecurity
 subdomain: web-application-security
 tags: