fix: resolve Windows test timeout in custom-system-prompt.spec.ts

- Replace toPosix() call with inline path normalization in mock implementation
- Handle both string and Buffer types for filePath parameter
- Normalize path separators to forward slashes for cross-platform compatibility
- Fixes test timeout issue on Windows CI environment

Author: roomote

src/core/prompts/__tests__/custom-system-prompt.spec.ts

@@ -122,10 +122,11 @@ describe("File-Based Custom System Prompt", () => {
 		const fileCustomSystemPrompt = "Custom system prompt from file"
 		// When called with utf-8 encoding, return a string
 		mockedFs.readFile.mockImplementation((filePath, options) => {
-			if (
-				filePath.toString().toPosix().includes(`.roo/system-prompt-${defaultModeSlug}`) &&
-				options === "utf-8"
-			) {
+			// Convert filePath to string and normalize path separators
+			const normalizedPath =
+				typeof filePath === "string" ? filePath.replace(/\\/g, "/") : filePath.toString().replace(/\\/g, "/")
+
+			if (normalizedPath.includes(`.roo/system-prompt-${defaultModeSlug}`) && options === "utf-8") {
 				return Promise.resolve(fileCustomSystemPrompt)
 			}
 			return Promise.reject({ code: "ENOENT" })
@@ -163,10 +164,11 @@ describe("File-Based Custom System Prompt", () => {
 		// Mock the readFile to return content from a file
 		const fileCustomSystemPrompt = "Custom system prompt from file"
 		mockedFs.readFile.mockImplementation((filePath, options) => {
-			if (
-				filePath.toString().toPosix().includes(`.roo/system-prompt-${defaultModeSlug}`) &&
-				options === "utf-8"
-			) {
+			// Convert filePath to string and normalize path separators
+			const normalizedPath =
+				typeof filePath === "string" ? filePath.replace(/\\/g, "/") : filePath.toString().replace(/\\/g, "/")
+
+			if (normalizedPath.includes(`.roo/system-prompt-${defaultModeSlug}`) && options === "utf-8") {
 				return Promise.resolve(fileCustomSystemPrompt)
 			}
 			return Promise.reject({ code: "ENOENT" })