修复分离状态跨平台原子替换

使用唯一临时文件并同步写入，避免 checkpoint 临时文件互相覆盖。

Unix 使用 rename，Windows 使用 MoveFileExW 原子覆盖已有 state.json。

拒绝符号链接和非普通文件目标，并增加覆盖已有目标回归测试。

apps/ai-game-creator-shell/src-tauri/src/ui_editor/commands/separation/persistence.rs

@@ -1,7 +1,9 @@
 use super::model::*;
 use crate::ui_editor::commands::separation::*;
-use std::fs;
+use std::fs::{self, OpenOptions};
+use std::io::Write;
 use std::path::{Path, PathBuf};
+use uuid::Uuid;
 
 const SEPARATION_STATE_MAX_BYTES: usize = 8 * 1024 * 1024;
 pub fn separation_sidecar_dir(root: &Path, asset_id: &str) -> Result<PathBuf, String> {
@@ -53,8 +55,8 @@ pub async fn write_separation_state(path: PathBuf, state: &SeparationState) -> R
             .map_err(|error| format!("序列化 separation state 失败：{error}"))?;
         write_separation_state_blocking(&path, &bytes)
     })
-        .await
-        .map_err(|error| format!("写入 separation state 任务失败：{error}"))?
+    .await
+    .map_err(|error| format!("写入 separation state 任务失败：{error}"))?
 }
 
 fn write_separation_state_blocking(path: &Path, bytes: &[u8]) -> Result<(), String> {
@@ -84,15 +86,40 @@ fn write_separation_state_blocking(path: &Path, bytes: &[u8]) -> Result<(), Stri
         app_log!("ui_separation.error stage=state_write reason=create_parent error={error}");
         format!("创建 separation sidecar 失败：{error}")
     })?;
-    let temporary = path.with_extension("json.tmp");
-    fs::write(&temporary, bytes).map_err(|error| {
+    match fs::symlink_metadata(path) {
+        Ok(metadata) if metadata.file_type().is_symlink() || !metadata.is_file() => {
+            app_log!("ui_separation.error stage=state_write reason=unsafe_target");
+            return Err("separation state 目标必须是普通文件".to_string());
+        }
+        Ok(_) => {}
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => {}
+        Err(error) => {
+            app_log!("ui_separation.error stage=state_write reason=target_metadata error={error}");
+            return Err(format!("检查 separation state 目标失败：{error}"));
+        }
+    }
+    let file_name = path
+        .file_name()
+        .and_then(|name| name.to_str())
+        .unwrap_or("state.json");
+    let temporary = parent.join(format!(".{file_name}.tmp.{}", Uuid::new_v4()));
+    let mut temporary_file = OpenOptions::new();
+    temporary_file.write(true).create_new(true);
+    let mut file = temporary_file.open(&temporary).map_err(|error| {
         app_log!("ui_separation.error stage=state_write reason=write_temp error={error}");
         format!("写入 separation state 失败：{error}")
     })?;
-    fs::rename(&temporary, path).map_err(|error| {
+    if let Err(error) = file.write_all(bytes).and_then(|_| file.sync_data()) {
+        let _ = fs::remove_file(&temporary);
+        app_log!("ui_separation.error stage=state_write reason=write_temp error={error}");
+        return Err(format!("写入 separation state 失败：{error}"));
+    }
+    drop(file);
+    if let Err(error) = replace_separation_state_atomically(&temporary, path) {
+        let _ = fs::remove_file(&temporary);
         app_log!("ui_separation.error stage=state_write reason=install error={error}");
-        format!("安装 separation state 失败：{error}")
-    })?;
+        return Err(format!("安装 separation state 失败：{error}"));
+    }
     app_log!(
         "ui_separation.state_write.completed file={} bytes={}",
         path.file_name()
@@ -105,6 +132,42 @@ fn write_separation_state_blocking(path: &Path, bytes: &[u8]) -> Result<(), Stri
     Ok(())
 }
 
+#[cfg(not(windows))]
+fn replace_separation_state_atomically(temporary: &Path, target: &Path) -> std::io::Result<()> {
+    fs::rename(temporary, target)
+}
+
+#[cfg(windows)]
+fn replace_separation_state_atomically(temporary: &Path, target: &Path) -> std::io::Result<()> {
+    use std::os::windows::ffi::OsStrExt;
+    use windows_sys::Win32::Storage::FileSystem::{
+        MOVEFILE_REPLACE_EXISTING, MOVEFILE_WRITE_THROUGH, MoveFileExW,
+    };
+
+    let source = temporary
+        .as_os_str()
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect::<Vec<_>>();
+    let destination = target
+        .as_os_str()
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect::<Vec<_>>();
+    let moved = unsafe {
+        MoveFileExW(
+            source.as_ptr(),
+            destination.as_ptr(),
+            MOVEFILE_REPLACE_EXISTING | MOVEFILE_WRITE_THROUGH,
+        )
+    };
+    if moved == 0 {
+        Err(std::io::Error::last_os_error())
+    } else {
+        Ok(())
+    }
+}
+
 pub fn read_separation_state(path: &Path) -> Result<SeparationState, String> {
     app_log!(
         "ui_separation.state_read.start file={}",
@@ -215,3 +278,23 @@ fn remove_separation_state(root: &Path, asset_id: &str) -> Result<(), String> {
         Err(error) => Err(format!("删除 separation state 失败：{error}")),
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn atomic_state_replacement_overwrites_existing_target() {
+        let directory = tempfile::tempdir().expect("create temporary state directory");
+        let target = directory.path().join("state.json");
+        let temporary = directory.path().join("state.json.tmp");
+        fs::write(&target, b"old").expect("write old state");
+        fs::write(&temporary, b"new").expect("write new state");
+
+        replace_separation_state_atomically(&temporary, &target)
+            .expect("replacement should overwrite existing state");
+
+        assert_eq!(fs::read(&target).expect("read replaced state"), b"new");
+        assert!(!temporary.exists());
+    }
+}