fix: address Phase 2 review — error handlers, drain queue, prevent listener accumulation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ts-protocol/commands.ts

@@ -62,12 +62,6 @@ export function decodeResponse(raw: string): Record<string, string>[] {
   });
 }
 
-export interface TS3Response {
-  errorId: number;
-  errorMessage: string;
-  data: Record<string, string>[];
-}
-
 export function parseErrorLine(line: string): { id: number; msg: string } {
   const decoded = decodeResponse(line.replace(/^error\s+/, ""))[0];
   return {