feat: 支持 uv 从 pyproject/requirements 创建虚拟环境

- 工作目录探测新增 pyproject.toml / requirements*.txt 扫描、uv 可用性与 can_create
- 新增 POST /api/v1/python/venv/create：已有虚拟环境优先复用；pyproject 走 uv sync，requirements 走 uv venv + uv pip install，并使用默认 PyPI 镜像
- 编辑器在缺少虚拟环境且具备依赖文件时显示「用 uv 创建环境」；没有 uv 或没有依赖文件时明确报错
- 解释器字段改为可选，留空由服务端默认 python.exe 并使用虚拟环境；Python 任务缺少虚拟环境/依赖文件时运行直接失败，不再回退系统解释器
- 补后端探测/创建测试、前端入口测试与 README

backend/tests/python_env_probe.rs

@@ -47,9 +47,22 @@ async fn fetch_token(app: &Router) -> String {
 }
 
 async fn post_probe(app: &Router, token: Option<&str>, payload: Value) -> (StatusCode, Value) {
+    post_json(app, "/api/v1/python/venv", token, payload).await
+}
+
+async fn post_create(app: &Router, token: Option<&str>, payload: Value) -> (StatusCode, Value) {
+    post_json(app, "/api/v1/python/venv/create", token, payload).await
+}
+
+async fn post_json(
+    app: &Router,
+    uri: &str,
+    token: Option<&str>,
+    payload: Value,
+) -> (StatusCode, Value) {
     let mut builder = Request::builder()
         .method("POST")
-        .uri("/api/v1/python/venv")
+        .uri(uri)
         .header(header::CONTENT_TYPE, "application/json");
     if let Some(token) = token {
         builder = builder.header("x-taskpilot-token", token);
@@ -68,7 +81,7 @@ async fn post_probe(app: &Router, token: Option<&str>, payload: Value) -> (Statu
         .into_body()
         .collect()
         .await
-        .expect("probe body should be readable")
+        .expect("response body should be readable")
         .to_bytes();
 
     (status, serde_json::from_slice(&body).unwrap_or(Value::Null))
@@ -179,3 +192,77 @@ async fn venv_probe_reports_missing_working_directory() {
             .contains("工作目录")
     );
 }
+
+#[tokio::test]
+async fn venv_probe_reports_project_dependency_files() {
+    let (app, temp_dir) = test_app().await;
+    let token = fetch_token(&app).await;
+    let project = temp_dir.path().join("deps-project");
+    fs::create_dir_all(&project).expect("project directory should be created");
+    fs::write(
+        project.join("pyproject.toml"),
+        "[project]\nname = \"demo\"\n",
+    )
+    .expect("pyproject.toml should be written");
+    fs::write(project.join("requirements.txt"), "").expect("requirements.txt should be written");
+
+    let (status, body) = post_probe(
+        &app,
+        Some(&token),
+        json!({
+            "working_dir": project.to_str().expect("project path should be UTF-8"),
+            "interpreter": "python.exe"
+        }),
+    )
+    .await;
+
+    assert_eq!(status, StatusCode::OK);
+    assert_eq!(body["status"], "missing");
+    assert_eq!(body["has_pyproject"], true);
+    assert_eq!(body["has_requirements"], true);
+    assert_eq!(body["requirements_files"], json!(["requirements.txt"]));
+    assert_eq!(body["can_create"], body["uv_available"]);
+}
+
+#[tokio::test]
+async fn venv_create_rejects_project_without_dependency_files() {
+    let (app, temp_dir) = test_app().await;
+    let token = fetch_token(&app).await;
+    let project = temp_dir.path().join("empty-project");
+    fs::create_dir_all(&project).expect("project directory should be created");
+
+    let (status, body) = post_create(
+        &app,
+        Some(&token),
+        json!({
+            "working_dir": project.to_str().expect("project path should be UTF-8")
+        }),
+    )
+    .await;
+
+    assert_eq!(status, StatusCode::BAD_REQUEST);
+    assert_eq!(body["code"], "VENV_CREATE_FAILED");
+    assert!(
+        body["message"]
+            .as_str()
+            .expect("message should be a string")
+            .contains("pyproject.toml")
+    );
+}
+
+#[tokio::test]
+async fn venv_create_requires_management_token() {
+    let (app, temp_dir) = test_app().await;
+
+    let (status, body) = post_create(
+        &app,
+        None,
+        json!({
+            "working_dir": temp_dir.path().to_str().expect("temp path should be UTF-8")
+        }),
+    )
+    .await;
+
+    assert_eq!(status, StatusCode::FORBIDDEN);
+    assert_eq!(body["code"], "FORBIDDEN");
+}

backend/tests/tasks.rs

@@ -113,6 +113,19 @@ fn script_task(id: &str, name: &str) -> Value {
     })
 }
 
+#[tokio::test]
+async fn empty_interpreter_defaults_to_python() {
+    let (app, _temp_dir) = test_app().await;
+    let mut payload = script_task("default_interpreter", "Default interpreter");
+    payload["action"]["interpreter"] = json!("");
+
+    let response = send_json(&app, Method::POST, "/api/v1/tasks", Some(payload)).await;
+
+    assert_eq!(response.status(), StatusCode::CREATED);
+    let created = response_json(response).await;
+    assert_eq!(created["action"]["interpreter"], "python.exe");
+}
+
 #[tokio::test]
 async fn task_crud_flow_works_end_to_end() {
     let (app, _temp_dir) = test_app().await;