Add session persistence and browser functionality

- Implement `StorageManager` for saving, loading, and managing sessions.
- Introduce platform-specific session directories for persistence.
- Add session browser UI for listing, loading, and deleting saved sessions.
- Enable AI-generated descriptions for session summaries.
- Update configurations to support storage settings and description generation.
- Extend README and tests to document and validate new functionality.

crates/owlen-core/src/config.rs

@@ -238,18 +238,20 @@ impl Default for UiSettings {
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct StorageSettings {
     #[serde(default = "StorageSettings::default_conversation_dir")]
-    pub conversation_dir: String,
+    pub conversation_dir: Option<String>,
     #[serde(default = "StorageSettings::default_auto_save")]
     pub auto_save_sessions: bool,
     #[serde(default = "StorageSettings::default_max_sessions")]
     pub max_saved_sessions: usize,
     #[serde(default = "StorageSettings::default_session_timeout")]
     pub session_timeout_minutes: u64,
+    #[serde(default = "StorageSettings::default_generate_descriptions")]
+    pub generate_descriptions: bool,
 }
 
 impl StorageSettings {
-    fn default_conversation_dir() -> String {
-        "~/.local/share/owlen/conversations".to_string()
+    fn default_conversation_dir() -> Option<String> {
+        None
     }
 
     fn default_auto_save() -> bool {
@@ -264,19 +266,35 @@ impl StorageSettings {
         120
     }
 
+    fn default_generate_descriptions() -> bool {
+        true
+    }
+
     /// Resolve storage directory path
+    /// Uses platform-specific data directory if not explicitly configured:
+    /// - Linux: ~/.local/share/owlen/sessions
+    /// - Windows: %APPDATA%\owlen\sessions
+    /// - macOS: ~/Library/Application Support/owlen/sessions
     pub fn conversation_path(&self) -> PathBuf {
-        PathBuf::from(shellexpand::tilde(&self.conversation_dir).as_ref())
+        if let Some(ref dir) = self.conversation_dir {
+            PathBuf::from(shellexpand::tilde(dir).as_ref())
+        } else {
+            // Use platform-specific data directory
+            dirs::data_local_dir()
+                .map(|d| d.join("owlen").join("sessions"))
+                .unwrap_or_else(|| PathBuf::from("./owlen_sessions"))
+        }
     }
 }
 
 impl Default for StorageSettings {
     fn default() -> Self {
         Self {
-            conversation_dir: Self::default_conversation_dir(),
+            conversation_dir: None, // Use platform-specific defaults
             auto_save_sessions: Self::default_auto_save(),
             max_saved_sessions: Self::default_max_sessions(),
             session_timeout_minutes: Self::default_session_timeout(),
+            generate_descriptions: Self::default_generate_descriptions(),
         }
     }
 }
@@ -340,3 +358,48 @@ pub fn ensure_ollama_config(config: &mut Config) -> &ProviderConfig {
 pub fn session_timeout(config: &Config) -> Duration {
     Duration::from_secs(config.storage.session_timeout_minutes.max(1) * 60)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_storage_platform_specific_paths() {
+        let config = Config::default();
+        let path = config.storage.conversation_path();
+
+        // Verify it contains owlen/sessions
+        assert!(path.to_string_lossy().contains("owlen"));
+        assert!(path.to_string_lossy().contains("sessions"));
+
+        // Platform-specific checks
+        #[cfg(target_os = "linux")]
+        {
+            // Linux should use ~/.local/share/owlen/sessions
+            assert!(path.to_string_lossy().contains(".local/share"));
+        }
+
+        #[cfg(target_os = "windows")]
+        {
+            // Windows should use AppData
+            assert!(path.to_string_lossy().contains("AppData"));
+        }
+
+        #[cfg(target_os = "macos")]
+        {
+            // macOS should use ~/Library/Application Support
+            assert!(path.to_string_lossy().contains("Library/Application Support"));
+        }
+
+        println!("Config conversation path: {}", path.display());
+    }
+
+    #[test]
+    fn test_storage_custom_path() {
+        let mut config = Config::default();
+        config.storage.conversation_dir = Some("~/custom/path".to_string());
+
+        let path = config.storage.conversation_path();
+        assert!(path.to_string_lossy().contains("custom/path"));
+    }
+}