feat: complete reference coverage and UX improvements

Reference pages:
- Add min-width, min-height, border-collapse to Box Model
- Add blockquote to Text Content
- Add new Semantic Inline section (time, mark, small, abbr, kbd, sub, sup, ins, del)

UX improvements:
- Rename "Free Coding" to "HTML & CSS Editor" in Playground
- Keep Welcome and Playground modules always expanded in sidebar

🤖 Generated with [Claude Code](https://claude.com/claude-code)

lessons/98-playground.json

@@ -1,7 +1,7 @@
 {
 	"$schema": "../schemas/code-crispies-module-schema.json",
 	"id": "playground",
-	"title": "HTML & CSS Editor",
+	"title": "Playground",
 	"description": "Experiment freely with HTML and CSS",
 	"mode": "playground",
 	"difficulty": "beginner",
@@ -9,7 +9,7 @@
 	"lessons": [
 		{
 			"id": "sandbox",
-			"title": "Editor",
+			"title": "HTML & CSS Editor",
 			"mode": "playground",
 			"description": "",
 			"task": "",