fix: prevent task output loss when mixing sync and async tasks

Fixes #4137

When processing async tasks, `_process_async_tasks` returns a new list
containing only async task outputs. The caller was replacing the existing
`task_outputs` list instead of extending it, causing all previous sync
task outputs to be silently lost.

Changed assignment (`=`) to `extend()` at all affected locations:
- `_execute_tasks()` lines 1155, 1169
- `_aexecute_tasks()` lines 960, 976
- `_handle_conditional_task()` line 1182
- `_ahandle_conditional_task()` line 990

This ensures sync task outputs accumulated before async tasks are
preserved when async tasks are collected.

Author: Rakshit-gen

lib/crewai/src/crewai/crew.py

@@ -957,9 +957,9 @@ async def _aexecute_tasks(
                 pending_tasks.append((task, async_task, task_index))
             else:
                 if pending_tasks:
-                    task_outputs = await self._aprocess_async_tasks(
+                    task_outputs.extend(await self._aprocess_async_tasks(
                         pending_tasks, was_replayed
-                    )
+                    ))
                     pending_tasks.clear()
 
                 context = self._get_context(task, task_outputs)
@@ -973,7 +973,7 @@ async def _aexecute_tasks(
                 self._store_execution_log(task, task_output, task_index, was_replayed)
 
         if pending_tasks:
-            task_outputs = await self._aprocess_async_tasks(pending_tasks, was_replayed)
+            task_outputs.extend(await self._aprocess_async_tasks(pending_tasks, was_replayed))
 
         return self._create_crew_output(task_outputs)
 
@@ -987,7 +987,7 @@ async def _ahandle_conditional_task(
     ) -> TaskOutput | None:
         """Handle conditional task evaluation using native async."""
         if pending_tasks:
-            task_outputs = await self._aprocess_async_tasks(pending_tasks, was_replayed)
+            task_outputs.extend(await self._aprocess_async_tasks(pending_tasks, was_replayed))
             pending_tasks.clear()
 
         return check_conditional_skip(
@@ -1152,7 +1152,7 @@ def _execute_tasks(
                 futures.append((task, future, task_index))
             else:
                 if futures:
-                    task_outputs = self._process_async_tasks(futures, was_replayed)
+                    task_outputs.extend(self._process_async_tasks(futures, was_replayed))
                     futures.clear()
 
                 context = self._get_context(task, task_outputs)
@@ -1166,7 +1166,7 @@ def _execute_tasks(
                 self._store_execution_log(task, task_output, task_index, was_replayed)
 
         if futures:
-            task_outputs = self._process_async_tasks(futures, was_replayed)
+            task_outputs.extend(self._process_async_tasks(futures, was_replayed))
 
         return self._create_crew_output(task_outputs)
 
@@ -1179,7 +1179,7 @@ def _handle_conditional_task(
         was_replayed: bool,
     ) -> TaskOutput | None:
         if futures:
-            task_outputs = self._process_async_tasks(futures, was_replayed)
+            task_outputs.extend(self._process_async_tasks(futures, was_replayed))
             futures.clear()
 
         return check_conditional_skip(