Limit server-wide decoded control requests to 16 and gate Stream Install providers behind a separate two-slot semaphore. The provider permit remains held through producer cleanup, bounding concurrent unrar work while ordinary bulk transfers retain their own capacity.
Test Plan:
- just test (passed after rerunning one transient ETXTBSY failure)
- just fmt (Rust formatting passed; repository's generated security report still triggers pre-existing rumdl violations)
- git diff --check
ddidderr
ff962801ae