feat: add MCP/skill tool protocol, tasks/tools pages, chat UX overhaul

Tools page: skill & MCP server management with [[skill:]]/[[mcp:]] protocol (up to 3 rounds). New Tasks and Tools pages. Chat: session snapshots, empty-session reuse, per-message model_id, unified JSON prediction suggestions. Settings: upload size limit, prediction options, model enable/disable. Schema additions with ensure_column migrations. Add FEATURES/ARCHITECTURE docs.

crates/engine/src/lib.rs

@@ -5,5 +5,5 @@ pub mod types;
 
 pub use error::{EngineError, Result};
 pub use manager::EngineManager;
-pub use remote::{stream_chat_remote, RemoteConfig};
+pub use remote::{chat_remote, stream_chat_remote, RemoteConfig};
 pub use types::{ChatMessage, ChatRequest, ChatStreamEvent, EngineConfig, EngineStatus};

crates/engine/src/manager.rs

@@ -271,6 +271,11 @@ pub(crate) fn sse_text_stream(
                             .or_else(|| value.get("content").and_then(|v| v.as_str()));
                         if let Some(text) = content {
                             yield Ok(ChatStreamEvent::Text(text.to_string()));
+                        } else if let Some(reasoning) = value
+                            .pointer("/choices/0/delta/reasoning_content")
+                            .and_then(|v| v.as_str())
+                        {
+                            yield Ok(ChatStreamEvent::Reasoning(reasoning.to_string()));
                         }
                     }
                     Err(e) => {

crates/engine/src/remote.rs

@@ -33,6 +33,32 @@ pub async fn stream_chat_remote(
     Ok(sse_text_stream(response.bytes_stream()))
 }
 
+/// 调用远程 OpenAI 兼容 API 并返回完整的非流式文本。
+pub async fn chat_remote(cfg: &RemoteConfig, req: ChatRequest) -> Result<String> {
+    let base = normalize_base(&cfg.base_url);
+    let url = format!("{base}/chat/completions");
+    let client = reqwest::Client::new();
+    let mut builder = client.post(&url).json(&req);
+    if let Some(key) = &cfg.api_key {
+        if !key.trim().is_empty() {
+            builder = builder.bearer_auth(key);
+        }
+    }
+    let response = builder.send().await?;
+    let status = response.status();
+    if !status.is_success() {
+        let body = response.text().await.unwrap_or_default();
+        return Err(EngineError::EngineHttp(status, body));
+    }
+    let value: serde_json::Value = response.json().await?;
+    let text = value
+        .pointer("/choices/0/message/content")
+        .and_then(|v| v.as_str())
+        .unwrap_or_default()
+        .to_string();
+    Ok(text)
+}
+
 /// 把用户填写的 base url 归一化为 `<scheme>://<host>/v1` 形式。
 fn normalize_base(base: &str) -> String {
     let mut s = base.trim().trim_end_matches('/').to_string();

crates/engine/src/types.rs

@@ -55,6 +55,8 @@ impl Serialize for ChatMessage {
 #[derive(Debug, Clone)]
 pub enum ChatStreamEvent {
     Text(String),
+    /// 推理模型（如 Qwen3.5/DeepSeek-R1）的思考过程增量文本
+    Reasoning(String),
     Usage {
         prompt_tokens: u32,
         completion_tokens: u32,