Flow marked as DELETE is not removed when promoting the whole branch

## Problem

When promoting an entire work item branch, a Flow component marked with the `DELETE` operation is included in the Change List, but the Flow is not deleted from the target org.

## Example

- Work item: `WI-004089`
- Branch: `salesforce/WI-004089`
- Work item title: `SF-3960 Optimize & deconflict Task triggers (before/after-save flows + Apex)`
- Target stage: Integration
- Deleted component: `Task_Trigger`
- Metadata type: `Flow`
- Operation displayed in the Change List: `DELETE`

The work item was promoted successfully, and the other Flow changes were deployed, but `Task_Trigger` remained present in the target org.

## Steps to reproduce

1. Create or use a Flow in the source environment.
2. Delete the Flow and include the deletion in a work item.
3. Verify that the Change List displays the Flow with operation `DELETE`.
4. Promote the entire work item branch to the next stage.
5. Check the target org after the promotion completes.

## Actual behavior

The promotion completes, but the deleted Flow still exists in the target org.

## Expected behavior

A Flow displayed in the work item Change List with operation `DELETE` should be deployed as a destructive change and removed from the target org when the whole branch is promoted.

## Additional context

The deletion is correctly detected and visible in DevOps Center before promotion. This is therefore different from cases where deleted metadata is not surfaced in the Change List at all.

The attached screenshot shows `Task_Trigger` with metadata type `Flow` and operation `DELETE` before the promotion.

Reproduce the promotion using a work item with a deleted Flow such as Task_Trigger, then compare the Change List with the target org after promoting the whole branch. Trace the branch-promotion handling for DELETE operations; done means the Flow is deployed as a destructive change and no longer exists in the target org.

Written by the indexing model from the issue text.