The python FastAPI sidecars have lived ad-hoc at /mnt/cache/appdata/
<engine>/build/ on Lucy without version control. Bringing them into
the skald repo so the engine code travels with the cross-engine
routing it depends on.
This commit lands the VANILLA version of each engine on main:
engines/f5-tts/ SWivid F5-TTS (CC-BY-NC weights flagged)
engines/kokoro/ hexgrad Kokoro-82M (Apache 2.0 top to bottom)
engines/tortoise/ neonbjb Tortoise-TTS (Apache 2.0 top to bottom)
Engine-specific kludges (question doubling, GPU coordination,
pause-duration tuning) get layered on engine/* branches per the
README. Main stays the safe-to-read baseline.
