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.

README.md

@@ -42,7 +42,9 @@ The OWLEN interface features a clean, multi-panel layout with vim-inspired navig
 - **Visual Selection & Clipboard** - Yank/paste text across panels
 - **Flexible Scrolling** - Half-page, full-page, and cursor-based navigation
 - **Model Management** - Interactive model and provider selection (press `m`)
-- **Session Management** - Start new conversations, clear history
+- **Session Persistence** - Save and load conversations to/from disk
+- **AI-Generated Descriptions** - Automatic short summaries for saved sessions
+- **Session Management** - Start new conversations, clear history, browse saved sessions
 - **Thinking Mode Support** - Dedicated panel for extended reasoning content
 - **Bracketed Paste** - Safe paste handling for multi-line content
 
@@ -139,6 +141,15 @@ cargo build --release --bin owlen-code --features code-client
 - `:m` / `:model` - Open model selector
 - `:n` / `:new` - Start new conversation
 - `:h` / `:help` - Show help
+- `:save [name]` / `:w [name]` - Save current conversation
+- `:load` / `:open` - Browse and load saved sessions
+- `:sessions` / `:ls` - List saved sessions
+
+**Session Browser** (accessed via `:load` or `:sessions`):
+- `j` / `k` / `↑` / `↓` - Navigate sessions
+- `Enter` - Load selected session
+- `d` - Delete selected session
+- `Esc` - Close browser
 
 ### Panel Management
 - Three panels: Chat, Thinking, and Input
@@ -164,6 +175,22 @@ base_url = "http://localhost:11434"
 timeout = 300
 ```
 
+### Storage Settings
+
+Sessions are saved to platform-specific directories by default:
+- **Linux**: `~/.local/share/owlen/sessions`
+- **Windows**: `%APPDATA%\owlen\sessions`
+- **macOS**: `~/Library/Application Support/owlen/sessions`
+
+You can customize this in your config:
+
+```toml
+[storage]
+# conversation_dir = "~/custom/path"  # Optional: override default location
+max_saved_sessions = 25
+generate_descriptions = true  # AI-generated summaries for saved sessions
+```
+
 Configuration is automatically saved when you change models or providers.
 
 ## Repository Layout
@@ -226,9 +253,10 @@ cargo fmt
 - [x] Bracketed paste support
 
 ### In Progress
+- [x] Session persistence (save/load conversations)
 - [ ] Theming options and color customization
 - [ ] Enhanced configuration UX (in-app settings)
-- [ ] Chat history management (save/load/export)
+- [ ] Conversation export (Markdown, JSON, plain text)
 
 ### Planned
 - [ ] Code Client Enhancement