New workspaces grow in; config saves don't redraw everything or race; media peek skips the player in front

- A workspace Hyprland makes for a switch (createworkspacev2) grows into the row
  over the slide instead of appearing at full size; the window keeps the full
  room meanwhile.
- Every config.toml save restarted the colour Animation, and Animation::new
  runs its clock even from a colour to itself, so every window redrew for 0.4 s
  per save. The colours now only fade when they change.
- The file watch could read config.toml halfway through the shell's own save
  and reset settings to their defaults. Saves and rereads share one lock, the
  file is written to a new file and renamed over, and the shell's own saves
  are skipped by the watch.
- A song change or new player only pops the island when the focused window
  isn't that player's app (parse::same_app, tested).

src/config.rs

@@ -505,6 +505,17 @@ static VALUES: LazyLock<RwLock<HashMap<String, Value>>> = LazyLock::new(Default:
 // what was wrong in the file when it was last read, for the config window
 static ERRORS: Mutex<Vec<String>> = Mutex::new(Vec::new());
 
+/*
+ * config.toml as the shell last wrote or read it. every save and every reread holds
+ * this lock, so the file watch can't read a save halfway or undo a change it raced
+ * with (it once reset settings to their defaults that way), and skips the shell's own saves
+ */
+static WRITTEN: Mutex<String> = Mutex::new(String::new());
+
+fn written() -> std::sync::MutexGuard<'static, String> {
+    WRITTEN.lock().unwrap_or_else(PoisonError::into_inner)
+}
+
 // ponytail: a lock and a hash lookup per call, a few hundred a frame; a snapshot struct if a profile ever shows it
 fn get<T: Setting>(path: &str, default: impl FnOnce() -> T) -> T {
     VALUES.read().unwrap_or_else(PoisonError::into_inner).get(path).and_then(T::read).unwrap_or_else(default)
@@ -520,17 +531,37 @@ pub fn option(path: &str) -> Option<&'static Opt> {
 
 // at startup: config.toml, or the first time, one made from the old shell.conf
 pub fn load() {
+    let mut written = written();
+
     let text = fs::read_to_string(file()).unwrap_or_else(|_| {
         migrate();
 
         let text = render();
 
-        let _ = fs::write(file(), &text);
+        let _ = write_file(&text);
 
         text
     });
 
     apply_text(&text);
+
+    *written = text;
+}
+
+// config.toml changed on disk: a hand edit applies, the shell's own saves are skipped. whether it applied
+pub fn reread() -> bool {
+    let mut written = written();
+    let text = fs::read_to_string(file()).unwrap_or_default();
+
+    if text == *written {
+        return false;
+    }
+
+    apply_text(&text);
+
+    *written = text;
+
+    true
 }
 
 // shell.conf's four settings, moved to their places in config.toml
@@ -667,26 +698,42 @@ pub fn override_of(path: &str) -> Option<Value> {
 pub fn set(path: &str, value: Value) -> Result<(), String> {
     check(path, &value)?;
 
+    let mut written = written();
+
     VALUES.write().unwrap_or_else(PoisonError::into_inner).insert(path.to_string(), value);
 
-    save()
+    save(&mut written)
 }
 
 // back to the default (a Hyprland option: back to Hyprland's own config)
 pub fn reset(path: &str) -> Result<(), String> {
+    let mut written = written();
+
     VALUES.write().unwrap_or_else(PoisonError::into_inner).remove(path);
 
-    save()
+    save(&mut written)
 }
 
-fn save() -> Result<(), String> {
-    fs::write(file(), render()).map_err(|error| format!("couldn't write {}: {error}", file().display()))?;
+fn save(written: &mut String) -> Result<(), String> {
+    let text = render();
+
+    write_file(&text).map_err(|error| format!("couldn't write {}: {error}", file().display()))?;
+
+    *written = text;
 
     theme::touch();
 
     Ok(())
 }
 
+// whole or not at all: a new file renamed over the old, so no reader sees half of it
+fn write_file(text: &str) -> std::io::Result<()> {
+    let fresh = file().with_extension("toml.new");
+
+    fs::write(&fresh, text)?;
+    fs::rename(&fresh, file())
+}
+
 // config.toml as the shell writes it: every setting with its help, then the Hyprland options set here
 pub fn render() -> String {
     let mut out = String::from(