feat: model multi-output workspace ownership

crates/ferese-core/src/lib.rs

@@ -1,3 +1,5 @@
+mod output;
 mod workspace;
 
+pub use output::{OutputError, OutputGeometry, OutputId, OutputWorkspaceMap, WorkspaceSwitch};
 pub use workspace::{WindowPlacement, Workspace, WorkspaceError, WorkspaceId, WorkspaceSet};