fix(persist): use XDG paths on macOS

Config and state now live in ~/.config/soulseek-rs and
~/.local/share/soulseek-rs instead of Application Support.

soulseek-rs/src/persist/paths.rs

@@ -1,3 +1,4 @@
+#[cfg(not(target_os = "macos"))]
 use directories::ProjectDirs;
 use std::path::PathBuf;
 
@@ -9,7 +10,7 @@ pub fn config_file() -> Option<PathBuf> {
     if let Ok(dir) = std::env::var("SOULSEEK_CONFIG_DIR") {
         return Some(PathBuf::from(dir).join("config.toml"));
     }
-    project_dirs().map(|d| d.config_dir().join("config.toml"))
+    config_dir().map(|d| d.join("config.toml"))
 }
 
 #[must_use]
@@ -17,9 +18,41 @@ pub fn state_dir() -> Option<PathBuf> {
     if let Ok(dir) = std::env::var("SOULSEEK_STATE_DIR") {
         return Some(PathBuf::from(dir));
     }
-    project_dirs().map(|d| d.data_dir().join("state"))
+    data_dir().map(|d| d.join("state"))
 }
 
+// macOS follows the XDG layout (~/.config, ~/.local/share) instead of
+// Application Support, by request. Other platforms keep the crate defaults.
+#[cfg(target_os = "macos")]
+fn config_dir() -> Option<PathBuf> {
+    xdg_dir("XDG_CONFIG_HOME", ".config")
+}
+
+#[cfg(target_os = "macos")]
+fn data_dir() -> Option<PathBuf> {
+    xdg_dir("XDG_DATA_HOME", ".local/share")
+}
+
+#[cfg(target_os = "macos")]
+fn xdg_dir(env: &str, fallback: &str) -> Option<PathBuf> {
+    let base = match std::env::var_os(env) {
+        Some(dir) if !dir.is_empty() => PathBuf::from(dir),
+        _ => directories::UserDirs::new()?.home_dir().join(fallback),
+    };
+    Some(base.join("soulseek-rs"))
+}
+
+#[cfg(not(target_os = "macos"))]
+fn config_dir() -> Option<PathBuf> {
+    project_dirs().map(|d| d.config_dir().to_path_buf())
+}
+
+#[cfg(not(target_os = "macos"))]
+fn data_dir() -> Option<PathBuf> {
+    project_dirs().map(|d| d.data_dir().to_path_buf())
+}
+
+#[cfg(not(target_os = "macos"))]
 fn project_dirs() -> Option<ProjectDirs> {
     ProjectDirs::from("", "", "soulseek-rs")
 }