fix: address Phase 3 review — Logger type export, PlayerEvents interface, PCM backpressure

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

src/logger.ts

@@ -2,7 +2,9 @@ import pino from "pino";
 import { mkdirSync } from "node:fs";
 import { join } from "node:path";
 
-export function createLogger(logDir?: string): pino.Logger {
+export type Logger = pino.Logger;
+
+export function createLogger(logDir?: string): Logger {
   if (!logDir) {
     return pino({ level: "info" });
   }