fix: address minor review findings N3, N5, N6

- N3: Type deleteClientRegistration param as TokenMethods['deleteTokens']
  instead of Promise<unknown>
- N5: Elevate deletion failure logging from debug to warn for operator
  visibility when stale client cleanup fails
- N6: Use getLogPrefix() instead of hardcoded log prefix to respect
  system-user privacy convention

packages/api/src/mcp/MCPConnectionFactory.ts

@@ -362,7 +362,7 @@ export class MCPConnectionFactory {
                 serverName: this.serverName,
                 deleteTokens: this.tokenMethods.deleteTokens,
               }).catch((err) => {
-                logger.debug(`${this.logPrefix} Failed to clear stale client registration`, err);
+                logger.warn(`${this.logPrefix} Failed to clear stale client registration`, err);
               });
             }
             const oldState = oldMeta?.state;

packages/api/src/mcp/oauth/tokens.ts

@@ -484,7 +484,7 @@ export class MCPTokenStorage {
   }: {
     userId: string;
     serverName: string;
-    deleteTokens: (query: { userId: string; type: string; identifier: string }) => Promise<unknown>;
+    deleteTokens: TokenMethods['deleteTokens'];
   }): Promise<void> {
     const identifier = `mcp:${serverName}`;
     await deleteTokens({
@@ -492,9 +492,8 @@ export class MCPTokenStorage {
       type: 'mcp_oauth_client',
       identifier: `${identifier}:client`,
     });
-    logger.debug(
-      `[MCPTokenStorage] Cleared stored client registration for ${serverName} (userId: ${userId})`,
-    );
+    const logPrefix = this.getLogPrefix(userId, serverName);
+    logger.debug(`${logPrefix} Cleared stored client registration`);
   }
 
   /**