refactor: shorten lesson titles and improve content

- Shorten verbose lesson titles for better sidebar display
- Minor content improvements across lessons

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lessons/26-html-data-attributes.json

@@ -1,7 +1,7 @@
 {
 	"$schema": "../schemas/code-crispies-module-schema.json",
 	"id": "html-data-attributes",
-	"title": "Custom Data Attributes",
+	"title": "Data Attrs",
 	"description": "Store custom data on HTML elements with data-* attributes",
 	"mode": "html",
 	"difficulty": "beginner",