Fix trajectory group duplication in gather_trajectory_groups (#312)

The after_each callback in gather_trajectory_groups was causing group
duplication by appending returned groups to the existing processed_groups
list. This resulted in both the original groups and the groups returned
by the callback being included in the final result.

Fixed by resetting processed_groups to an empty list before collecting
the after_each callback results, ensuring only the callback-returned
groups are included in the final output.


Amp-Thread-ID: https://ampcode.com/threads/T-46ce9369-cd67-44ca-b963-75c14498132e

Co-authored-by: Amp <[email protected]>

Author: corbt

src/art/gather.py

@@ -48,6 +48,7 @@ async def gather_trajectory_groups(
         ae_processed_groups = await asyncio.gather(
             *(after_each(g) for g in processed_groups)
         )
+        processed_groups = []
         for g in ae_processed_groups:
             if g is None:
                 continue