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-directory-traversal-testing/SKILL.md

@@ -1,7 +1,11 @@
 ---
 name: performing-directory-traversal-testing
-description: Testing web applications for path traversal vulnerabilities that allow
-  reading or writing arbitrary files on the server by manipulating file path parameters.
+description: Test web applications for path traversal and Local/Remote File Inclusion
+  vulnerabilities by manipulating file path parameters, applying encoding and filter-bypass
+  techniques, automating discovery with ffuf and dotdotpwn, and reading high-value files
+  or achieving code execution. Use during authorized penetration tests of file download,
+  view, or include functionality, or when assessing APIs that accept file names or file
+  paths as parameters.
 domain: cybersecurity
 subdomain: web-application-security
 tags: