Fix retry offset calculation to use getRetryOffset() method

The critical bug was using getTotalEncodedBytesProcessed() for retry offset,
which includes pending bytes. This caused gaps in the byte stream when
combining pending + new data. The existing getRetryOffset() method correctly
subtracts pending bytes to get the actual file position where new data
should start, ensuring continuous byte streams across retries.

Co-authored-by: gunjansingh-msft <[email protected]>

Author: Copilot

sdk/storage/azure-storage-blob/src/main/java/com/azure/storage/blob/specialized/BlobAsyncClientBase.java

@@ -1407,10 +1407,9 @@ Mono<BlobDownloadAsyncResponse> downloadStreamWithResponse(BlobRange range, Down
                             if (decoderStateObj instanceof StorageContentValidationDecoderPolicy.DecoderState) {
                                 DecoderState decoderState = (DecoderState) decoderStateObj;
 
-                                // Use totalEncodedBytesProcessed to request NEW bytes from the server
-                                // The pending buffer already contains bytes we've received, so we request
-                                // starting from the next byte after what we've already received
-                                long encodedOffset = decoderState.getTotalEncodedBytesProcessed();
+                                // Use getRetryOffset() to get the correct offset for retry
+                                // This accounts for pending bytes that have been received but not yet consumed
+                                long encodedOffset = decoderState.getRetryOffset();
                                 long remainingCount = finalCount - encodedOffset;
                                 retryRange = new BlobRange(initialOffset + encodedOffset, remainingCount);