Test hook: simulates the user accepting the current selection.
Test hook: simulates the QuickPick being dismissed (Escape, focus loss, ...).
Test hook: simulates the user typing into the filter box.
Test hook: simulates clicking a title-bar button (e.g. the back button).
Test hook: simulates clicking a per-item button.
Creates a scriptable QuickPick-shaped object with event subscription removal and the same synchronous hide/dispose model as the higher-level fake. It does not filter/rank items, validate selection rules, or model focus and keyboard behavior. Exact Extension Host event scheduling is outside this mock.