format: apply repo prettier (3.8.1) to the folded skills tree

963 markdown files reformatted with the repository's pinned prettier so
pnpm format:check covers the folded tree like every other repo file.

The formatter's embedded-language pass also normalized code fences
(TS semicolons, closed HTML tags in examples, lowercased CSS hex colors,
one renumbered list that skipped an index). Alphanumeric token deltas vs
the fold commit were audited file-by-file; all are formatter-equivalent
markup normalizations plus the four sanitized skills.

packages/mosaic/framework/skills/web-design-guidelines/SKILL.md

@@ -3,7 +3,7 @@ name: web-design-guidelines
 description: Review UI code for Web Interface Guidelines compliance. Use when asked to "review my UI", "check accessibility", "audit design", "review UX", or "check my site against best practices".
 metadata:
   author: vercel
-  version: "1.0.0"
+  version: '1.0.0'
   argument-hint: <file-or-pattern>
 ---
 
@@ -31,6 +31,7 @@ Use WebFetch to retrieve the latest rules. The fetched content contains all the
 ## Usage
 
 When a user provides a file or pattern argument:
+
 1. Fetch guidelines from the source URL above
 2. Read the specified files
 3. Apply all rules from the fetched guidelines