[studio] Make FilePickerPopup accept on double click of a file

src/olympic/studio/modlib/include/studio/filepickerpopup.hpp

@@ -13,7 +13,11 @@ class FilePickerPopup {
 
 	private:
 		ox::String m_name;
-		FileExplorer m_explorer;
+		struct Explorer: public FileExplorer {
+			mutable bool opened{};
+			explicit Explorer(keel::Context &kctx);
+			void fileOpened(ox::StringViewCR path) const noexcept override;
+		} m_explorer;
 		ox::Vector<ox::String> const m_fileExts;
 		bool m_open{};
 
@@ -33,6 +37,10 @@ class FilePickerPopup {
 
 		ox::Optional<ox::String> draw(Context &ctx) noexcept;
 
+	private:
+		[[nodiscard]]
+		ox::Optional<ox::String> handlePick() noexcept;
+
 };
 
 }