消除 AGC 导出测试对 HOME 环境变量的依赖

- export.rs：npm_export_tests 的 2 条用例（npm_package_contains_dist_project_root_assets_and_publish_readme、本批新增的 built_project_publish_payload_includes_uploaded_assets_and_prefers_dist_assets）不再用 std::env::var("HOME") 拼临时根，改用仓库既有约定的 crate::tests::canonical_test_tempdir
- 动机：Windows 只设 USERPROFILE、不设 HOME 时，std::env::var("HOME").unwrap() 会以 NotPresent panic；改后与本批另 5 条 publish_export_tests 的临时根口径一致
- 未动断言：两条用例的断言与语义保持不变，只替换临时根来源（canonical_test_tempdir 同样返回 tempfile::TempDir，root.path() 用法不变）
- 验证（同一命令 cargo test --locked --manifest-path apps/ai-game-creator-shell/src-tauri/Cargo.toml --bin genarrative-ai-game-creator-shell -- --test-threads=1 project::export::）：HOME 未设置（env -u HOME）→ exit 0，test result: ok. 12 passed; 0 failed；HOME=C:/Users/dongy → exit 0，test result: ok. 12 passed; 0 failed
- 顺带核对：project/verification.rs 仍有 1 处同名 HOME 写法，属其它模块范围，本次不动

apps/ai-game-creator-shell/src-tauri/src/project/export.rs

@@ -934,9 +934,9 @@ mod npm_export_tests {
 
     #[test]
     fn npm_package_contains_dist_project_root_assets_and_publish_readme() {
-        let base = PathBuf::from(std::env::var("HOME").unwrap()).join("data/tmp");
-        fs::create_dir_all(&base).unwrap();
-        let root = tempfile::tempdir_in(base).unwrap();
+        // 仓库约定的跨平台临时根（基于 std::env::temp_dir()）：不依赖 HOME，
+        // Windows 上只有 USERPROFILE 时同样可跑。
+        let root = crate::tests::canonical_test_tempdir("agc-npm-export-");
         for directory in [
             "dist/assets/uploads",
             "assets/uploads",
@@ -993,9 +993,8 @@ mod npm_export_tests {
 
     #[test]
     fn built_project_publish_payload_includes_uploaded_assets_and_prefers_dist_assets() {
-        let base = PathBuf::from(std::env::var("HOME").unwrap()).join("data/tmp");
-        fs::create_dir_all(&base).unwrap();
-        let root = tempfile::tempdir_in(base).unwrap();
+        // 与同批另 5 条 publish_export_tests 同口径：用仓库的跨平台临时根，不依赖 HOME。
+        let root = crate::tests::canonical_test_tempdir("agc-publish-payload-");
         for directory in [
             "dist/assets/uploads",
             "assets/uploads",