feat: add lesson export and import functionality

- Implemented `LessonExport` and `LessonImport` actions in the action module.
- Added corresponding command parsing for lesson export and import.
- Created functions to handle lesson export and import in the memory module.
- Updated state management to reflect changes after lesson operations.
- Introduced deferred operations for handling asynchronous tasks in the event loop.
- Enhanced the tool execution context to include graduated checks for file operations.
- Added OAuth support with PKCE for secure authorization flows.
- Implemented a loopback server for handling OAuth redirects.
- Refactored various modules to improve code organization and maintainability.

src/model/memory.rs

@@ -128,6 +128,33 @@ pub fn slug_path(memory_dir: &Path, raw: &str) -> PathBuf {
     memory_dir.join(if clean.is_empty() { "memory.md" } else { &clean })
 }
 
+pub fn export_lessons(memory_dir: &Path, output: &Path) -> std::io::Result<()> {
+    let names = Memory::list(memory_dir);
+    let lessons: Vec<Memory> = names.iter()
+        .filter_map(|n| Memory::read(memory_dir, n).ok())
+        .collect();
+    let data = serde_json::to_string_pretty(&lessons)
+        .map_err(std::io::Error::other)?;
+    std::fs::write(output, data)?;
+    Ok(())
+}
+
+pub fn import_lessons(memory_dir: &Path, input: &Path) -> std::io::Result<usize> {
+    let data = std::fs::read_to_string(input)?;
+    let lessons: Vec<Memory> = serde_json::from_str(&data)
+        .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?;
+    let existing: std::collections::HashSet<String> = Memory::list(memory_dir).into_iter().collect();
+    let mut imported = 0;
+    for lesson in &lessons {
+        let slug = Memory::slugify(&lesson.name).unwrap_or_default();
+        if !existing.contains(&slug) {
+            lesson.write(memory_dir)?;
+            imported += 1;
+        }
+    }
+    Ok(imported)
+}
+
 pub fn create_retrospective(session_dir: &Path, session: &Session, lessons: &[Memory]) -> std::io::Result<Memory> {
     let now = chrono::Utc::now().timestamp_millis();
     let lessons_content: String = lessons.iter()