feat(task-mcp): Add task_resolve_duplicate tool

Combines close + link operations for duplicate issues:
- Closes the duplicate task (sets status to completed)
- Creates bidirectional 'duplicates' link to dominant task

Usage: task_resolve_duplicate(duplicate_id, dominant_id)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/tools/index.ts

@@ -135,6 +135,18 @@ export const toolDefinitions = [
       required: ['item_id', 'checked'],
     },
   },
+  {
+    name: 'task_resolve_duplicate',
+    description: 'Resolve a duplicate issue by closing it and linking to the dominant issue',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        duplicate_id: { type: 'string', description: 'The duplicate task ID to close' },
+        dominant_id: { type: 'string', description: 'The dominant/original task ID to keep' },
+      },
+      required: ['duplicate_id', 'dominant_id'],
+    },
+  },
 
   // Epic Tools
   {