feat: add GitHub repository synchronization functionality with document extraction pipeline and update security policy to permit GitHub API access.

src/lib/extractionPipeline.js

@@ -26,6 +26,15 @@ ALWAYS return a valid JSON object in the following format:
 Return JSON only. No markdown blocks or other text.`;
 
 export async function processSourceText(textContent, sourceName) {
+  // Deduplicate: skip if a source with the same name was already successfully processed
+  const existing = await db.getSources();
+  const alreadyDone = existing.find(
+    s => s.name === sourceName && s.status === 'completed'
+  );
+  if (alreadyDone) {
+    throw new Error(`"${sourceName}" has already been processed. Delete the existing source first if you want to re-analyse it.`);
+  }
+
   const rec = await db.addSource({ name: sourceName, status: 'processing' });
   const sourceId = rec.id;
 
@@ -38,7 +47,8 @@ export async function processSourceText(textContent, sourceName) {
       const jsonStr = jsonMatch ? jsonMatch[0] : responseText;
       extractedData = JSON.parse(jsonStr);
     } catch (e) {
-      throw new Error('AI response was not valid JSON.');
+      console.error('[Pipeline] AI returned non-JSON response:', responseText?.substring(0, 500));
+      throw new Error(`AI response was not valid JSON. The model responded with: "${responseText?.substring(0, 120)}..."`);
     }
 
     await mergeKnowledgeGraph(extractedData);