Fix config upgrade failures, save races, lock confirmation and release validation (#23)

* Coordinate config writes and gate releases on desktop validation

* Use toolkit rc.2 with painting and session lock fixes

* Ignore retired desktop widget settings in existing configs

crates/ferese-theme-client/src/service.rs

@@ -90,6 +90,7 @@ mod tests {
                 ])
                 .env(CHILD, "1")
                 .env("XDG_RUNTIME_DIR", root.path())
+                .env_remove("FERESE_SOCKET")
                 .output()
                 .unwrap();
             assert!(