refactor(app): retire manual-save semantics (M13 D5)

- AppEngine: save_project -> export_project_path(explicit path);
  project_modified removed (write-through has no dirty flag)
- File menu's save/save-as are the export path (extension-dispatched
  ove/otio/fcpxml); the library row export path is unchanged
- facade project_save/is_modified stay frozen, documented as the
  legacy export surface
- docs: M13 D5 checked off; M12 inventory updated

src/app.rs

@@ -127,9 +127,9 @@ mod modal_ids {
 enum FileAction {
 	ImportFootage,
 	Open,
-	/// Export the current project to a file (`.ove` / `.otio` / `.fcpxml`,
-	/// dispatched by extension).
-	SaveAs,
+	/// Export the current project to a file (the 导出工程文件… action's
+	/// target; `.ove` / `.otio` / `.fcpxml`, dispatched by extension).
+	ExportProjectFile,
 	/// Import a project file into the library (the manager's 导入).
 	ImportProject,
 	/// Export the selected library project (the manager's 导出; the row's
@@ -525,7 +525,7 @@ impl<E: AppEngine> OakApp<E> {
 			OPEN_PROJECT => self.open_file_dialog(FileAction::Open, cx),
 			OPEN_FROM_LIBRARY | PROJECT_MANAGER => self.show_project_manager(cx),
 			IMPORT_FOOTAGE => self.open_file_dialog(FileAction::ImportFootage, cx),
-			EXPORT_PROJECT => self.open_file_dialog(FileAction::SaveAs, cx),
+			EXPORT_PROJECT => self.open_file_dialog(FileAction::ExportProjectFile, cx),
 			CLOSE => self
 				.engine
 				.update(cx, |engine, cx| engine.close_project(cx)),
@@ -610,17 +610,6 @@ impl<E: AppEngine> OakApp<E> {
 		}
 	}
 
-	/// Exports the project to a file (the 导出工程文件… action's target; the
-	/// format is dispatched by the picked path's extension).
-	fn save_project(&mut self, path: Option<PathBuf>, cx: &mut Context<Self>) {
-		let result = self
-			.engine
-			.update(cx, |engine, cx| engine.save_project(path, cx));
-		if let Err(err) = result {
-			println!("[file] save failed: {err}");
-		}
-	}
-
 	/// 新建项目: creates a blank project in the library and opens it (the
 	/// write-through persists it from the first edit). Falls back to the
 	/// engine's plain new-project path when the library is unavailable.
@@ -976,9 +965,9 @@ impl<E: AppEngine> OakApp<E> {
 
 	/// Opens the platform file dialog for `action` and routes the picked
 	/// path(s) through the engine. Open / Import use the path picker (import
-	/// footage allows multiple files); Save As and the manager's export ask
-	/// for a new path. The picker resolves asynchronously, so the chosen
-	/// path is applied in a spawned task via [`Self::on_file_paths`].
+	/// footage allows multiple files); the 导出工程文件… and the manager's
+	/// export ask for a new path. The picker resolves asynchronously, so the
+	/// chosen path is applied in a spawned task via [`Self::on_file_paths`].
 	fn open_file_dialog(&mut self, action: FileAction, cx: &mut Context<Self>) {
 		match action {
 			FileAction::Open | FileAction::ImportFootage | FileAction::ImportProject => {
@@ -1002,7 +991,7 @@ impl<E: AppEngine> OakApp<E> {
 				})
 				.detach();
 			}
-			FileAction::SaveAs => {
+			FileAction::ExportProjectFile => {
 				let current = self
 					.engine
 					.read(cx)
@@ -1024,7 +1013,7 @@ impl<E: AppEngine> OakApp<E> {
 				cx.spawn(async move |this, cx| {
 					if let Ok(Ok(Some(path))) = receiver.await {
 						this.update(cx, |this, cx| {
-							this.on_file_paths(FileAction::SaveAs, vec![path], cx);
+							this.on_file_paths(FileAction::ExportProjectFile, vec![path], cx);
 						});
 					}
 				})
@@ -1078,8 +1067,8 @@ impl<E: AppEngine> OakApp<E> {
 				Some(path) => engine.open_project_path(path.clone(), cx),
 				None => Ok(()),
 			},
-			FileAction::SaveAs => match paths.first() {
-				Some(path) => engine.save_project(Some(path.clone()), cx),
+			FileAction::ExportProjectFile => match paths.first() {
+				Some(path) => engine.export_project_path(path.clone(), cx),
 				None => Ok(()),
 			},
 			FileAction::ImportFootage => {

src/i18n.rs

@@ -323,7 +323,6 @@ const EN: &[(&str, &str)] = &[
 	("dialog.close", "Close"),
 	("file.open.title", "Open Project"),
 	("file.import_footage.title", "Import Footage"),
-	("file.save_as.title", "Save Project As"),
 	("preferences.title", "Preferences"),
 	("preferences.backend", "Renderer backend"),
 	("preferences.backend.placeholder", "Select a backend…"),
@@ -499,7 +498,6 @@ const ZH: &[(&str, &str)] = &[
 	("dialog.close", "关闭"),
 	("file.open.title", "打开项目"),
 	("file.import_footage.title", "导入素材"),
-	("file.save_as.title", "项目另存为"),
 	("preferences.title", "偏好设置"),
 	("preferences.backend", "渲染后端"),
 	("preferences.backend.placeholder", "选择一个后端…"),

src/oakui/engine.rs

@@ -298,9 +298,6 @@ pub trait AppEngine:
 	/// Steps the undo stack forward one entry.
 	fn redo(&mut self, cx: &mut Context<Self>);
 
-	/// Whether the project has unsaved changes.
-	fn project_modified(&self) -> bool;
-
 	/// Starts a new blank project with a single default sequence.
 	fn new_project(&mut self, cx: &mut Context<Self>);
 
@@ -309,10 +306,12 @@ pub trait AppEngine:
 	/// interchange loader.
 	fn open_project_path(&mut self, path: PathBuf, cx: &mut Context<Self>) -> Result<(), String>;
 
-	/// Saves the project to `path` (or its own filename when `None`). The
-	/// format is dispatched by extension like [`open_project_path`]
-	/// (AppEngine::open_project_path).
-	fn save_project(&mut self, path: Option<PathBuf>, cx: &mut Context<Self>)
+	/// Exports the current project to the file `path` (the 导出工程文件…
+	/// action's target). The format is dispatched by extension like
+	/// [`open_project_path`] (AppEngine::open_project_path). Exporting is a
+	/// pure file write — the write-through library already persists every
+	/// edit, so there is no "save" anymore.
+	fn export_project_path(&mut self, path: PathBuf, cx: &mut Context<Self>)
 		-> Result<(), String>;
 
 	/// Closes the current project, leaving the app with no sequence.

src/oakui/ffi.rs

@@ -358,11 +358,11 @@ unsafe extern "C" {
 		err: *mut c_char,
 		err_size: c_int,
 	) -> c_int;
-	/// `oakengine_project_save` — save to `path` (or the recorded
-	/// filename when NULL).
+	/// `oakengine_project_save` — write the project to `path` (or the
+	/// recorded filename when NULL). Legacy manual-save ABI, now used only
+	/// as the .ove export path (导出工程文件…); the write-through library is
+	/// the primary persistence.
 	pub fn oakengine_project_save(self_: *mut OakEngineProject, path: *const c_char) -> c_int;
-	/// `oakengine_project_is_modified`.
-	pub fn oakengine_project_is_modified(self_: *const OakEngineProject) -> c_int;
 	/// `oakengine_project_name` (buf/size).
 	pub fn oakengine_project_name(
 		self_: *const OakEngineProject,

src/oakui/mock.rs

@@ -1302,10 +1302,6 @@ impl AppEngine for MockEngine {
 		cx.notify();
 	}
 
-	fn project_modified(&self) -> bool {
-		false
-	}
-
 	fn new_project(&mut self, cx: &mut Context<Self>) {
 		println!("[mock engine] new project: demo data stays (mock mode)");
 		cx.notify();
@@ -1322,12 +1318,8 @@ impl AppEngine for MockEngine {
 		Ok(())
 	}
 
-	fn save_project(
-		&mut self,
-		_path: Option<PathBuf>,
-		cx: &mut Context<Self>,
-	) -> Result<(), String> {
-		println!("[mock engine] save: no persistence in mock mode");
+	fn export_project_path(&mut self, _path: PathBuf, cx: &mut Context<Self>) -> Result<(), String> {
+		println!("[mock engine] export: no persistence in mock mode");
 		cx.notify();
 		Ok(())
 	}

src/oakui/real.rs

@@ -580,8 +580,6 @@ pub struct RealEngine {
 	/// the selection changes or the project is dropped — the renderer binds
 	/// the footage node, so a new selection must bind the new node.
 	source_renderer: Mutex<RendererSlot>,
-	/// Whether the project has unsaved changes (mirrors the facade flag).
-	modified: bool,
 }
 
 impl RealEngine {
@@ -656,7 +654,6 @@ impl RealEngine {
 			cpu_frame_cache: Mutex::new(HashMap::new()),
 			renderer: Mutex::new(RendererSlot::Untried),
 			source_renderer: Mutex::new(RendererSlot::Untried),
-			modified: false,
 		}
 	}
 
@@ -987,7 +984,6 @@ impl RealEngine {
 			},
 			path,
 		};
-		self.modified = unsafe { oakengine_project_is_modified(project) != 0 };
 
 		// The sequence: the project's first, or a blank default.
 		let count = unsafe { oakengine_project_sequence_count(project) };
@@ -1019,7 +1015,6 @@ impl RealEngine {
 		self.tracks.clear();
 
 		self.sequence_info = None;
-		self.modified = false;
 		self.project_info = Project {
 			name: UNTITLED.into(),
 			path: PathBuf::new(),
@@ -1398,7 +1393,6 @@ impl RealEngine {
 		self.rebuild_timeline();
 		// The sequence content changed: cached rendered frames are stale.
 		self.cpu_frame_cache.lock().unwrap().clear();
-		self.modified = true;
 		cx.notify();
 	}
 
@@ -2154,7 +2148,6 @@ impl AppEngine for RealEngine {
 			self.refresh_sequence_info();
 			self.rebuild_timeline();
 			self.cpu_frame_cache.lock().unwrap().clear();
-			self.modified = true;
 			cx.notify();
 		}
 	}
@@ -2167,15 +2160,10 @@ impl AppEngine for RealEngine {
 			self.refresh_sequence_info();
 			self.rebuild_timeline();
 			self.cpu_frame_cache.lock().unwrap().clear();
-			self.modified = true;
 			cx.notify();
 		}
 	}
 
-	fn project_modified(&self) -> bool {
-		self.modified
-	}
-
 	fn new_project(&mut self, cx: &mut Context<Self>) {
 		let project = unsafe { oakengine_project_create() };
 		if project.is_null() {
@@ -2201,28 +2189,22 @@ impl AppEngine for RealEngine {
 		}
 	}
 
-	fn save_project(
+	fn export_project_path(
 		&mut self,
-		path: Option<PathBuf>,
+		path: PathBuf,
 		cx: &mut Context<Self>,
 	) -> Result<(), String> {
 		if self.project_ptr().is_none() {
 			return Err("no project open".into());
 		}
 		let ext = path
-			.as_ref()
-			.and_then(|p| p.extension())
+			.extension()
 			.and_then(|e| e.to_str())
 			.map(|e| e.to_ascii_lowercase());
-		let result = match ext.as_deref() {
-			Some("otio") | Some("fcpxml") => self.save_interchange(&path.unwrap(), cx),
-			_ => self.save_ove(path.as_deref(), cx),
-		};
-		if result.is_ok() {
-			self.modified = false;
-			cx.notify();
+		match ext.as_deref() {
+			Some("otio") | Some("fcpxml") => self.export_interchange(&path, cx),
+			_ => self.export_ove(&path, cx),
 		}
-		result
 	}
 
 	fn close_project(&mut self, cx: &mut Context<Self>) {
@@ -2586,22 +2568,22 @@ impl RealEngine {
 		}
 	}
 
-	/// Saves to the project's own filename (or `path`) through the OVE
-	/// serializer.
-	fn save_ove(&mut self, path: Option<&Path>, _cx: &mut Context<Self>) -> Result<(), String> {
+	/// Exports the project to `path` through the OVE serializer (the .ove
+	/// branch of 导出工程文件…; the write-through library stays the primary
+	/// persistence, this only writes a file).
+	fn export_ove(&mut self, path: &Path, _cx: &mut Context<Self>) -> Result<(), String> {
 		let Some(project) = self.project_ptr() else {
 			return Err("no project open".into());
 		};
-		let cpath = path.and_then(cstr_path);
-		let ptr = cpath
-			.as_ref()
-			.map(|c| c.as_ptr())
-			.unwrap_or(std::ptr::null());
-		let rc = unsafe { oakengine_project_save(project, ptr) };
+		let Some(cpath) = cstr_path(path) else {
+			return Err("invalid project path".into());
+		};
+		let rc = unsafe { oakengine_project_save(project, cpath.as_ptr()) };
 		if rc != 0 {
-			return Err(format!("failed to save the project (error {rc})"));
+			return Err(format!("failed to export the project (error {rc})"));
 		}
-		// The facade recorded the target filename; refresh the display name.
+		// The facade records the target filename (legacy save side effect);
+		// refresh the display name to match.
 		let name = read_string(|buf, size| unsafe { oakengine_project_name(project, buf, size) });
 		if !name.is_empty() {
 			self.project_info.name = name;
@@ -2614,9 +2596,9 @@ impl RealEngine {
 		Ok(())
 	}
 
-	/// Saves as `.otio` / `.fcpxml` through the oaktask save task (the
+	/// Exports as `.otio` / `.fcpxml` through the oaktask save task (the
 	/// facade derives the output filename from the project's own filename).
-	fn save_interchange(&mut self, path: &PathBuf, _cx: &mut Context<Self>) -> Result<(), String> {
+	fn export_interchange(&mut self, path: &PathBuf, _cx: &mut Context<Self>) -> Result<(), String> {
 		let Some(project) = self.project_ptr() else {
 			return Err("no project open".into());
 		};
@@ -2635,7 +2617,7 @@ impl RealEngine {
 		let error = Self::task_error(task);
 		unsafe { oakengine_task_free(task) };
 		if rc == 0 {
-			return Err(format!("failed to save \"{}\": {error}", path.display()));
+			return Err(format!("failed to export \"{}\": {error}", path.display()));
 		}
 		self.project_info.path = path.clone();
 		Ok(())