Support TFLite CLI on Windows

[betweentwomidnights]

Summary

• Allow the TFLite CLI to start on Windows when the POSIX-only termios and tty modules are unavailable.
• Preserve the existing arrow-key picker on POSIX platforms; Windows uses the picker’s existing numeric fallback when an interactive selection is needed.

Root cause

sa3_tflite.py imported termios and tty unconditionally, which prevented any Windows invocation from reaching inference, including fully non-interactive commands that supply --dit and --decoder.

Validation

• python -m py_compile optimized/tflite/scripts/sa3_tflite.py
• Native Windows LiteRT/XNNPACK text-to-audio smoke test (20 s, one step).
• Native Windows LiteRT/XNNPACK end-to-end generation with sm-sfx/same-s (20 s, eight steps, CFG 1.0): completed in 12.85 s and produced a verified 44.1 kHz stereo PCM WAV.

The POSIX import succeeds unchanged on Linux/macOS, so the existing arrow-key path remains in use there.