fix(#388): address PR review findings — fix WebSocket/REST bugs, improve error handling, fix types and comments

Critical fixes:
- Fix FormData field name mismatch (audio -> file) to match backend FileInterceptor
- Add /speech namespace to WebSocket connection URL
- Pass auth token in WebSocket handshake options
- Wrap audio.play() in try-catch for NotAllowedError and DOMException handling
- Replace bare catch block with named error parameter and descriptive message
- Add connect_error and disconnect event handlers to WebSocket
- Update JSDoc to accurately describe batch transcription (not real-time partial)

Important fixes:
- Emit transcription-error before disconnect in gateway auth failures
- Capture MediaRecorder error details and clean up media tracks on error
- Change TtsDefaultConfig.format type from string to AudioFormat
- Define canonical SPEECH_TIERS and AUDIO_FORMATS arrays as single source of truth
- Fix voice count from 54 to 53 in provider, AGENTS.md, and docs
- Fix inaccurate comments (Piper formats, tier prop, SpeachesProvider, TextValidationPipe)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/speech/speech.config.ts

@@ -12,6 +12,7 @@
  */
 
 import { registerAs } from "@nestjs/config";
+import type { AudioFormat } from "./interfaces/speech-types";
 
 // ==========================================
 // Default values
@@ -58,7 +59,7 @@ export interface TtsDefaultConfig {
   enabled: boolean;
   url: string;
   voice: string;
-  format: string;
+  format: AudioFormat;
 }
 
 export interface TtsPremiumConfig {
@@ -247,7 +248,7 @@ export function getSpeechConfig(): SpeechConfig {
         enabled: isTtsEnabled(),
         url: process.env.TTS_DEFAULT_URL ?? TTS_DEFAULT_DEFAULTS.url,
         voice: process.env.TTS_DEFAULT_VOICE ?? TTS_DEFAULT_DEFAULTS.voice,
-        format: process.env.TTS_DEFAULT_FORMAT ?? TTS_DEFAULT_DEFAULTS.format,
+        format: (process.env.TTS_DEFAULT_FORMAT ?? TTS_DEFAULT_DEFAULTS.format) as AudioFormat,
       },
       premium: {
         enabled: isTtsPremiumEnabled(),