Fix task instance display in task group grid view

[yimingpeng]

closes: #55319

Problem Summary

When checking the status of a task group in the grid view:

1. The header only shows the # of abstract tasks in mapped task group (e..g, 3 tasks instead of 40 tasks).
2. The task instances list has no results. (This will be addressed in a separate MR)

Proposed Solution

For Issue 1

• When child nodes have child_states (mapped tasks), now we expand and count each state of individual task instances rather than treating them as one abstract task

### For Issue 2
- First we check whether the task name pattern is a task group ID
- Next we resolve this pattern to all task ids within the group
- So whenever we encounter a task group, we query task instances by filtering on the task ids extracted from last step other than using the original name pattern.

After the Fix

Screen.Recording.2025-09-17.at.9.04.56.PM.mp4

Running result on 2025-10-29

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[pierrejeambrun]

Thanks for the PR.

A few comments to address.

For 1 - I think it's nice just a few comments but we're almost there.

For 2 - I think there is a problem. Basically the issue comes from prefix_group_id=False in the group definition of the Dag. And could be also caused by overriding the display_name of tasks contained in the group. Because we are searching over task_display_name and the only way it will match is if the group id prefix is contained in the field we are filtering on the db side. The implementation you made here is not great because it's not handled on the db side but use the serialized dag and also because it mixes 'task_display_namesearch andtask_id` search. I would split this PR and move 2 - changes to a different PR so it doesn't block this one.

[pierrejeambrun]

@yimingpeng Any chance you can address the comments so we can go ahead and merge resolution for 1?

[yimingpeng]

Hi @pierrejeambrun , yes and sorry, a bit busy lately, will work on this soonish, thanks 🙏

[pierrejeambrun]

Looking nice, just one nit and we should be good to go.

[jason810496]

Thanks for the fix!

[github-actions]

Backport successfully created: v3-1-test

Status	Branch	Result
✅	v3-1-test