`promoteCompletedStreamToHotCache` — wraps the `promote_stream_cache_to_hot_cache`
Rust IPC, forwards the resolved path + size into `useHotCacheStore` as a
`'stream-promote'` entry — moves into `src/store/promoteStreamCache.ts`.
File-private with four call sites; no caller-side changes outside
playerStore's own import.
9 focused tests pin the payload shape (incl. the `'mp3'` suffix fallback
and the null customDir pass-through), the success path that records the
entry, the early-returns for null / empty path, the `size || 0` fallback,
and the silent error swallow.
playerStore 3207 → 3189 LOC.
Frank Stellmacher