feat: add JSON export support to Theia

- Added JSON format button to ExportConfigModal with 📦 icon
- Added 'json' to valid formats list in validateAndMergeConfig
- JSON export available for courses (outputs raw CourseData structure)
- Enables round-trip workflow: export JSON → upload → continue

Author: JasonWarrenUK

src/lib/components/theia/ExportConfigModal.svelte

@@ -238,6 +238,15 @@
           >
             🌐 HTML
           </button>
+          <button
+            type="button"
+            class="format-tab"
+            class:active={format === "json"}
+            on:click={() => (format = "json")}
+            disabled={isExporting}
+          >
+            📦 JSON
+          </button>
           <button
             type="button"
             class="format-tab disabled"

src/lib/services/theiaService.ts

@@ -211,7 +211,7 @@ export function validateAndMergeConfig(config: Partial<ExportConfig>): ExportCon
 	}
 
 	// Validate format
-	const validFormats: ExportFormat[] = ['markdown', 'html', 'pdf'];
+	const validFormats: ExportFormat[] = ['markdown', 'html', 'json', 'pdf'];
 	if (!validFormats.includes(merged.format)) {
 		throw new Error(`Invalid format: ${merged.format}`);
 	}