tests: assemble the OFX fixture bundle correctly on Windows

The fixture plugin binary was copied into Contents/Linux-x86-64 under
the extension-less name "plugin" on every non-macOS platform. On
Windows the host never loads it: LoadLibrary appends .dll to
extension-less module names, so the scan found the bundle but produced
no plugin — and because the (passing) draw-overlay test scans first,
the path dedupe then hid the failure from the lifecycle test, which
died with "interact variant instance: NotFound". Use Contents/Win64
and plugin.dll on Windows in both bundle assembly sites.

crates/oakplugin/tests/common/mod.rs

@@ -52,12 +52,20 @@ pub fn test_plugin_dir() -> Option<PathBuf> {
 				.join("oak-test-plugin.ofx.bundle");
 			let platform = if cfg!(target_os = "macos") {
 				"MacOS"
+			} else if cfg!(target_os = "windows") {
+				"Win64"
 			} else {
 				"Linux-x86-64"
 			};
 			let bin_dir = bundle.join("Contents").join(platform);
 			std::fs::create_dir_all(&bin_dir).ok()?;
-			let target = bin_dir.join("plugin");
+			// Windows 上必须有 .dll 扩展名：LoadLibrary 会对无扩展名的
+			// 模块名自动追加 ".dll"，名为 "plugin" 的文件将加载失败。
+			let target = bin_dir.join(if cfg!(target_os = "windows") {
+				"plugin.dll"
+			} else {
+				"plugin"
+			});
 			if !target.exists() {
 				std::fs::copy(&lib, &target).ok()?;
 			}

src/oakui/ofx.rs

@@ -798,12 +798,20 @@ mod tests {
 			.join("oak-test-plugin.ofx.bundle");
 		let platform = if cfg!(target_os = "macos") {
 			"MacOS"
+		} else if cfg!(target_os = "windows") {
+			"Win64"
 		} else {
 			"Linux-x86-64"
 		};
 		let bin_dir = bundle.join("Contents").join(platform);
 		std::fs::create_dir_all(&bin_dir).ok()?;
-		let target = bin_dir.join("plugin");
+		// Windows needs the .dll extension: LoadLibrary appends ".dll" to
+		// extension-less module names, so a bare "plugin" file never loads.
+		let target = bin_dir.join(if cfg!(target_os = "windows") {
+			"plugin.dll"
+		} else {
+			"plugin"
+		});
 		if !target.exists() {
 			std::fs::copy(&lib, &target).ok()?;
 		}