Workpackages created from another in the Gantt panel are one day shorter than expected

[ncouvert]

Workpackages created from another in the Gantt panel are one day shorter than expected.
In the example below, the created workpackage lasts two days instead of three.

Expected

The created workpackage should have the same duration as the original one.

[ncouvert]

Depends on this PR :

• Nco/releng/sw 2026 3 #37