feat: add editing and MCP command handling, enhance SSE streaming with usage tracking

- Implemented `Edit` and `McpAdd` commands in the command parser and handler.
- Added a new `stream` module to the runtime for handling streaming events.
- Enhanced `SseParser` to parse usage information from SSE events.
- Introduced `ToolCallAccumulator` for tracking tool calls independently.
- Updated `AppStateRest` to include `app_config` and `MiscState` to track `effort_level` and `selected_index`.
- Modified `LlmClient` to support streaming responses with usage tracking.
- Improved error handling and retry logic in the streaming API calls.
- Added tests for new features and improved markdown rendering in the chat view.

src/app/subagent/engine.rs

@@ -32,7 +32,7 @@ pub fn run_subagent(ctx: SubagentContext, tx: mpsc::Sender<SubagentEvent>) -> an
         let api_key = std::env::var("API_KEY").unwrap_or_default();
         let model = std::env::var("MODEL").unwrap_or_default();
 
-        let client = crate::service::provider::LlmClient::new(api_key, model);
+        let client = crate::service::provider::LlmClient::new(api_key, model, None);
         let response = match client.chat(&messages) {
             Ok(r) => r,
             Err(e) => {