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)

src/helpers/renderer.js

@@ -37,6 +37,11 @@ export function renderModuleList(container, modules, onSelectModule, onSelectLes
 		moduleContainer.classList.add("module-container");
 		moduleContainer.dataset.moduleId = module.id;
 
+		// Keep welcome and playground modules always expanded
+		if (module.id === "welcome" || module.id === "playground") {
+			moduleContainer.open = true;
+		}
+
 		// Create module header using <summary>
 		const moduleHeader = document.createElement("summary");
 		moduleHeader.classList.add("module-list-item", "module-header");