Fix Copilot issues: update fromJWT docs and remove TokenCallback duplication

- Updated Token.fromJWT() documentation to reflect that it handles
  decoding failures gracefully instead of throwing errors
- Removed duplicate TokenCallback type definition from IDBSQLClient.ts
- Now imports TokenCallback from ExternalTokenProvider.ts to maintain
  a single source of truth

Author: madhav-db

lib/connection/auth/tokenProvider/Token.ts

@@ -98,10 +98,11 @@ export default class Token {
 
   /**
    * Creates a Token from a JWT string, extracting the expiration time from the payload.
+   * If the JWT cannot be decoded, the token is created without expiration info.
+   * The server will validate the token anyway, so decoding failures are handled gracefully.
    * @param jwt - The JWT token string
    * @param options - Additional token options (tokenType, refreshToken, scopes)
-   * @returns A new Token instance with expiration extracted from the JWT
-   * @throws Error if the JWT cannot be decoded
+   * @returns A new Token instance with expiration extracted from the JWT (if available)
    */
   static fromJWT(
     jwt: string,

lib/contracts/IDBSQLClient.ts

@@ -4,16 +4,12 @@ import IAuthentication from '../connection/contracts/IAuthentication';
 import { ProxyOptions } from '../connection/contracts/IConnectionOptions';
 import OAuthPersistence from '../connection/auth/DatabricksOAuth/OAuthPersistence';
 import ITokenProvider from '../connection/auth/tokenProvider/ITokenProvider';
+import { TokenCallback } from '../connection/auth/tokenProvider/ExternalTokenProvider';
 
 export interface ClientOptions {
   logger?: IDBSQLLogger;
 }
 
-/**
- * Type for the callback function that retrieves tokens from external sources.
- */
-export type TokenCallback = () => Promise<string>;
-
 type AuthOptions =
   | {
       authType?: 'access-token';