test: add queue UUID path coverage in LocalQueueTests

- Add test_markRetry_works_with_queue_item_id (uses queue UUID not eventId)
- Update test_markDead_after_max_retries to use queue item id from batch
- Fixes review finding: tests previously only used eventId, not queue UUID

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

AIStudyApp/AIStudyAppTests/LocalQueueTests.swift

@@ -54,12 +54,28 @@ final class LocalQueueTests: XCTestCase {
         XCTAssertTrue(true)
     }
 
+    func test_markRetry_works_with_queue_item_id() {
+        let item = makeItem(eventId: "evt-lq-id-001")
+        queue.enqueue([item], userId: "user-test")
+        // Use queue item id (UUID) instead of eventId
+        guard let queueId = queue.fetchPendingBatch(limit: 10, userId: "user-test").first?.id else {
+            XCTFail("Expected at least one pending item")
+            return
+        }
+        queue.markRetry(ids: [queueId])
+        XCTAssertTrue(true, "markRetry should accept queue item UUID")
+    }
+
     func test_markDead_after_max_retries() {
         let item = makeItem(eventId: "evt-lq-004")
         queue.enqueue([item], userId: "user-test")
-        // Simulate multiple retries
+        guard let queueId = queue.fetchPendingBatch(limit: 10, userId: "user-test").first?.id else {
+            XCTFail("Expected pending item")
+            return
+        }
+        // Simulate multiple retries using queue item UUID
         for _ in 0..<5 {
-            queue.markRetry(ids: ["evt-lq-004"])
+            queue.markRetry(ids: [queueId])
         }
         // After exceeding maxRetryCount (3), status should be .dead
         let pending = queue.fetchPendingBatch(limit: 10, userId: "user-test")