Include total_blocks in content_block:end events

Orchestrator now includes total_blocks count in content_block:end event data,
allowing hooks to determine which block is the last in the response.

This enables hooks to display token usage after the last content block from
each LLM response, rather than after every block or only at the end.

Changes:
- Added total_blocks to CONTENT_BLOCK_START event data
- Added total_blocks to CONTENT_BLOCK_END event data
- Hooks can now check: is_last = block_index == total_blocks - 1

🤖 Generated with [Amplifier](https://github.com/microsoft/amplifier)

Co-Authored-By: Amplifier <240397093+microsoft-amplifier@users.noreply.github.com>

Author: bkrabach

amplifier_module_loop_basic/__init__.py

@@ -174,7 +174,8 @@ async def execute(
                     f"Response has content_blocks: {content_blocks is not None} - count: {len(content_blocks) if content_blocks else 0}"
                 )
                 if content_blocks:
-                    logger.info(f"Emitting events for {len(content_blocks)} content blocks")
+                    total_blocks = len(content_blocks)
+                    logger.info(f"Emitting events for {total_blocks} content blocks")
                     for idx, block in enumerate(content_blocks):
                         logger.info(f"Emitting CONTENT_BLOCK_START for block {idx}, type: {block.type.value}")
                         # Emit block start (without non-serializable raw object)
@@ -183,11 +184,16 @@ async def execute(
                             {
                                 "block_type": block.type.value,
                                 "block_index": idx,
+                                "total_blocks": total_blocks,
                             },
                         )
 
-                        # Emit block end with complete block and usage
-                        event_data = {"block_index": idx, "block": block.to_dict()}
+                        # Emit block end with complete block, usage, and total count
+                        event_data = {
+                            "block_index": idx,
+                            "total_blocks": total_blocks,
+                            "block": block.to_dict(),
+                        }
                         if usage:
                             event_data["usage"] = usage.model_dump() if hasattr(usage, "model_dump") else usage
                         await hooks.emit(CONTENT_BLOCK_END, event_data)