TTS-024: Implement CLI Audio File Output

[murdore]

Summary

Implement CLI logic to save TTS audio to files when --tts-output flag is provided.

Technical Details

• File(s): src/cli/commands/generate.ts, src/cli/commands/stream.ts
• Effort: 2h

Acceptance Criteria

• [ ] Check if --tts-output flag is provided
• [ ] Extract TTSResult from GenerateResult.audio
• [ ] Call provider.saveAudioToFile(audio, outputPath)
• [ ] Display success message with file path and size
• [ ] Handle errors gracefully
• [ ] Support both absolute and relative paths
• [ ] Create parent directories if needed
• [ ] Works for both generate and stream commands
• [ ] Integration test: CLI saves audio file correctly

Dependencies

• Depends on: TTS-022, TTS-023
• Blocks: none

Priority: medium | Effort: 2h | Complexity: simple