Fix 3 bug standalone: save project lỗi schema, export MIDI/WAV không hỏi nơi lưu

- Bug 1: serializeTracksList bỏ section item không có sectionId (do insertSectionAtPlayhead tạo) — tránh source_data {} làm schema oneOf fail
- Bug 2: export MIDI qua save-dialog + write file, toast kèm đường dẫn
- Bug 3: export mix WAV/MP3/OGG qua save-dialog + write file, toast kèm đường dẫn
- Marker tauri_bridge_ready: xóa khi window destroy + guard SF_PARENT_PID — tránh standalone treo 120s

src-tauri/src/lib.rs

@@ -648,6 +648,40 @@ pub fn run() {
                             waited_ms += 100;
                         }
                     }
+                    // ── Native Save-As dialog bridge (export MIDI/WAV) ──
+                    // Giong pick_dir: engine ghi ipc/save_file.request (chua ten
+                    // mac dinh) → thread mo NATIVE SaveFileDialog → ghi ket qua
+                    // vao ipc/save_file.response. Frontend lay path → POST bytes
+                    // /api/v1/files/write → file thuc su duoc ghi vao noi chon.
+                    let sreq = ipc_dir_for_thread.join("save_file.request");
+                    if sreq.exists() {
+                        let default_name = std::fs::read_to_string(&sreq).unwrap_or_default();
+                        let _ = std::fs::remove_file(&sreq);
+                        let sresp = ipc_dir_for_thread.join("save_file.response");
+                        let _ = std::fs::remove_file(&sresp);
+                        let handle = app_handle.clone();
+                        let sresp_for_main = sresp.clone();
+                        let handle_for_closure = handle.clone();
+                        let _ = handle.run_on_main_thread(move || {
+                            let saved: Option<FilePath> = handle_for_closure
+                                .dialog()
+                                .file()
+                                .set_file_name(default_name.trim())
+                                .blocking_save_file();
+                            let val = saved
+                                .map(|p| match p {
+                                    FilePath::Path(pb) => pb.to_string_lossy().to_string(),
+                                    FilePath::Url(u) => u.to_string(),
+                                })
+                                .unwrap_or_default();
+                            let _ = std::fs::write(&sresp_for_main, val);
+                        });
+                        let mut s_waited_ms = 0u32;
+                        while !sresp.exists() && s_waited_ms < 300_000 {
+                            std::thread::sleep(std::time::Duration::from_millis(100));
+                            s_waited_ms += 100;
+                        }
+                    }
                     std::thread::sleep(std::time::Duration::from_millis(150));
                 }
             });
@@ -687,6 +721,16 @@ pub fn run() {
                 // phu/an giu event loop song, Tauri khong tu exit; exit(0)
                 // ket thuc dut diem (pump da dung, khong con respawn bridge).
                 if window.label() == "main" {
+                    // Xoa marker bridge khi app tat han — neu de lai, lan sau
+                    // chay engine STANDALONE se nham tuong co bridge va cho
+                    // response khong bao gio den (treo 120s truoc fallback).
+                    let appdata = std::env::var("APPDATA").unwrap_or_else(|_| ".".into());
+                    let _ = std::fs::remove_file(
+                        std::path::Path::new(&appdata)
+                            .join("SonicForgeDAW")
+                            .join("ipc")
+                            .join("tauri_bridge_ready"),
+                    );
                     // Orphan sweep: bat CA dau engine con song theo image name —
                     // engine spawn thu cong (khong co SF_PARENT_PID), engine cua
                     // lan chay truoc bi crash, hoac engine song sot khi app chet