feat: add JavaScript lesson section with starter lessons and sidebar section grouping headers

Implementation following plan:
- S01: Update JSON schema to support 'javascript' mode
- S02: Install @codemirror/lang-javascript dependency
- S03: Define JavaScript section in sections.js
- S04: Create 3 JavaScript lesson JSON files (variables, DOM, events)
- S05: Add JavaScript validation support in validator.js
- S06: Add JavaScript preview rendering in LessonEngine.js
- S07: Add JavaScript CodeMirror mode and editor config
- S08: Register JavaScript modules in all language stores
- S09: Add JavaScript section to landing page, navigation, and app config
- S10: Add sidebar section grouping headers with category mapping
- S11: Update tests for JavaScript mode and section headers

schemas/code-crispies-module-schema.json

@@ -19,8 +19,8 @@
 		},
 		"mode": {
 			"type": "string",
-			"enum": ["css", "tailwind", "html", "markdown"],
-			"description": "Whether this module teaches CSS, Tailwind, HTML, or Markdown"
+			"enum": ["css", "tailwind", "html", "markdown", "javascript"],
+			"description": "Whether this module teaches CSS, Tailwind, HTML, Markdown, or JavaScript"
 		},
 		"difficulty": {
 			"type": "string",
@@ -60,7 +60,7 @@
 					},
 					"mode": {
 						"type": "string",
-						"enum": ["css", "tailwind", "html", "markdown"],
+						"enum": ["css", "tailwind", "html", "markdown", "javascript"],
 						"description": "Override module mode for individual lessons"
 					},
 					"tailwindConfig": {