Export (CSV/JSON), label printing, and share flows all trigger `UIActivityViewController` via a SwiftUI `.sheet(item:)` binding from a view that is itself already presented as a sheet (Settings, a tag-editor sheet, a link-existing-item sheet). The share sheet **flashes and tears itself down within a single frame, with zero user interaction** — confirmed by the user ("I didn't tap anything"). The bug only reveals itself by tracing the actual runtime presentation hierarchy (which root view presents which screen as a sheet), not from reading the call site in isolation.
