/game/file only wrote SPIFFS (960 KB, too small for a voice pack). A
path prefixed sd/ (or /sdcard/) now routes to the microSD: the card is
mounted on demand (audio_ensure_sd, independent of hook state) and the
parent dir is created. MAX_BODY 256->512 KB so full say() hints fit
(streamed in 2 KB chunks, RAM-safe). Enable FATFS LFN_HEAP so >8.3
filenames work (greet_0142738200.wav etc). Validated: 40-sample FR
voice pack staged to /sdcard/voice on the bench PLIP (960 MB card).