fix(backend): fallback to DB query for AgentExecutorBlock output in dry-run

During dry-run, the sub-agent's output events may not reach the
event_bus listener before the GRAPH_EXEC_UPDATE arrives (the simulated
execution completes faster than events propagate). This causes the
AgentExecutorBlock to complete with 0 outputs.

Adds a DB fallback: after the event loop breaks on graph COMPLETED,
if no outputs were yielded, query get_node_executions for the
sub-agent's OUTPUT block results and yield them.

Evidence: normal run produces 1 output, ALL dry-runs produce 0.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

autogpt_platform/backend/backend/blocks/agent.py

@@ -163,6 +163,30 @@ class AgentExecutorBlock(Block):
                         extra_steps=event.stats.node_exec_count if event.stats else 0,
                     )
                 )
+
+                # Fallback for dry-run: if no outputs were yielded via events
+                # (common in simulation where events may arrive before listener),
+                # query the sub-agent's output nodes directly from the DB.
+                if not yielded_node_exec_ids:
+                    from backend.data.execution import get_node_executions
+
+                    results = await get_node_executions(
+                        graph_exec_id=graph_exec_id,
+                        statuses=[ExecutionStatus.COMPLETED],
+                    )
+                    for result in results:
+                        r_block = get_block(result.block_id)
+                        if not r_block or r_block.block_type != BlockType.OUTPUT:
+                            continue
+                        r_name = (result.input_data or {}).get("name")
+                        if not r_name:
+                            continue
+                        for r_data in (result.output_data or {}).get("output", []):
+                            logger.debug(
+                                f"Execution {log_id} fallback output {r_name}: {r_data}"
+                            )
+                            yield r_name, r_data
+
                 break
 
             logger.debug(