examples/voxtral_tts: trim PR to public-facing files (align with qwen3_5_moe layout)

Internal docs, parity tooling, and developer-only test scripts move to the
voxtral-tts-dev branch. The PR now ships the same kind of files qwen3_5_moe
exposes publicly: model.py, export script, runner, CMake, README.

Removed (kept on voxtral-tts-dev):
  BENCHMARK.md, PROGRESS.md
  voxtral_tts_vs_voxtral_realtime_manager_note.md
  mermaid_architecture_voxtral_tts_parity_gap.md
  parity.py, compare_parity_traces.py
  test_cuda_parity.py, test_eager_e2e.py, test_export_cli.py,
  test_parity.py, test_validation_contract.py,
  test_verify_codec_export.py, test_verify_export_parity.py
  transcribe_apple_speech.swift, transcribe_parakeet.py
  verify_codec_export.py, verify_export_parity.py, verify_xnnpack_transcript.py

Updated README and run_cuda_e2e.sh to drop links to the moved files.

Authored with Claude (Anthropic) assistance.

Author: Young Han