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/app/runtime/stream/tools/mod.rs

@@ -0,0 +1,24 @@
+use crate::tool::{ToolCtx, all_tools};
+use serde_json::Value;
+use anyhow::Result;
+
+pub fn execute_tool_call(name: &str, args: &Value, ctx: &ToolCtx) -> Result<String> {
+    let tools = all_tools();
+    for tool in &tools {
+        if tool.name() == name {
+            return tool.run(ctx, args);
+        }
+    }
+    Err(anyhow::anyhow!("tool not found: {}", name))
+}
+
+#[expect(dead_code)]
+pub fn execute_deferred_tool(name: &str, args: &Value, ctx: &ToolCtx) -> Result<String> {
+    let tools = all_tools();
+    for tool in &tools {
+        if tool.name() == name {
+            return tool.run(ctx, args);
+        }
+    }
+    Err(anyhow::anyhow!("deferred tool not found: {}", name))
+}