[TimoKuronen]

Summary

• Split editor-apply flow into focused helpers and thread Catalog through sync/save paths in the Desktop ViewModel.
• Share selection-without-reload and clarify Save-gate / in-place grid refresh intent without changing product behavior.

Test plan

• dotnet test on Core, Application, and Infrastructure test projects: 118 passing
• Opening an existing catalog leaves Save disabled until the catalog is dirty with a known path; Save As remains available whenever a catalog is open
• Saving a dirty catalog with a known path writes that path and clears dirty/Save-enabled state
• Approving or invalidating a selected entry in a scrolled catalog keeps selection and does not jump the grid to the top
• Locale status text on the entry row stays in sync with effective status after editor apply / approve / invalidate