Add debug logging for segment boundary tracking and retry offsets

Added verbose logging to track:
- Segment completion with byte offsets in StructuredMessageDecoder
- Retry offset calculation in DecoderState
- Retry range in BlobAsyncClientBase for structured messages

This helps diagnose smart retry behavior and verify segment boundary alignment.

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

Author: Copilot

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

@@ -1413,6 +1413,10 @@ Mono<BlobDownloadAsyncResponse> downloadStreamWithResponse(BlobRange range, Down
                                 long remainingCount = finalCount - encodedOffset;
                                 retryRange = new BlobRange(initialOffset + encodedOffset, remainingCount);
 
+                                LOGGER.info(
+                                    "Structured message smart retry: resuming from offset {} (initial={}, encoded={})",
+                                    initialOffset + encodedOffset, initialOffset, encodedOffset);
+
                                 // Preserve the decoder state for the retry
                                 retryContext = retryContext
                                     .addData(Constants.STRUCTURED_MESSAGE_DECODER_STATE_CONTEXT_KEY, decoderState);

sdk/storage/azure-storage-common/src/main/java/com/azure/storage/common/implementation/structuredmessage/StructuredMessageDecoder.java

@@ -214,6 +214,7 @@ private void readSegmentFooter(ByteBuffer buffer) {
         // Mark that this segment is complete - update the last complete segment boundary
         // This is the position where we can safely resume if a retry occurs
         lastCompleteSegmentStart = messageOffset;
+        LOGGER.verbose("Segment {} complete at byte offset {}", currentSegmentNumber, lastCompleteSegmentStart);
 
         if (currentSegmentNumber == numSegments) {
             readMessageFooter(buffer);

sdk/storage/azure-storage-common/src/main/java/com/azure/storage/common/policy/StorageContentValidationDecoderPolicy.java

@@ -305,7 +305,9 @@ public long getTotalEncodedBytesProcessed() {
         public long getRetryOffset() {
             // Use the decoder's last complete segment start as the retry offset
             // This ensures we resume from a segment boundary, not mid-segment
-            return decoder.getLastCompleteSegmentStart();
+            long retryOffset = decoder.getLastCompleteSegmentStart();
+            LOGGER.verbose("Retry offset calculated: {} (last complete segment boundary)", retryOffset);
+            return retryOffset;
         }
 
         /**