refactor: improve type safety in file service and error handling

- Change listFiles() to synchronous method returning cached IDs
- Add type predicate to ApiError.isApiError() for better type narrowing
- Remove redundant ApiError union type in retry error handling

AIClasses/BaseAIFileService.ts

@@ -35,7 +35,7 @@ export abstract class BaseAIFileService implements IAIFileService {
 		this.fileIDs = await this.listFilesFromAPI();
 	}
 
-	public async listFiles(): Promise<string[]> {
+	public listFiles(): string[] {
 		return [...this.fileIDs];
 	}
 
@@ -78,7 +78,7 @@ export abstract class BaseAIFileService implements IAIFileService {
 
 	// Retries operation on retryable errors (500, 502, 503, 504) with exponential backoff
 	protected async withRetry<T>(operationName: string, operation: () => Promise<T>): Promise<T> {
-		let lastError: ApiError | unknown;
+		let lastError: unknown;
 
 		for (let attempt = 1; attempt <= BaseAIFileService.MAX_RETRIES; attempt++) {
 			try {

AIClasses/IAIFileService.ts

@@ -2,7 +2,7 @@ import type { Attachment } from "Conversations/Attachment";
 
 export interface IAIFileService {
     refreshCache(): Promise<void>;
-    listFiles(): Promise<string[]>;
+    listFiles(): string[];
     uploadFile(attachment: Attachment): Promise<string>;
     deleteFile(attachment: Attachment): Promise<void>;
 }

Types/ApiError.ts

@@ -23,7 +23,7 @@ export class ApiError extends Error {
         this.name = "ApiError";
     }
 
-    static isApiError(error: unknown): boolean {
+    static isApiError(error: unknown): error is ApiError {
         return error instanceof ApiError;
     }