feat: relibc S1 — sem_open refcounting + glibc cross-reference assessment

Phase S1 (Critical Correctness):
- sem_open/sem_close: global refcounting via BTreeMap + AtomicUsize
- sem_close: decrements refcount, munmaps only at zero
- sem_open: reuses existing mapping, O_EXCL returns EEXIST
- sem_unlink: marks entry for removal before shm_unlink
- va_list parsing: reads mode_t and value from stack after oflag
- All 11 sem_* functions verified in libc.so T

Phase S2-S4 (Designed, documented):
- eventfd() function, signalfd read path, EINTR handling
- name canonicalization, cancellation safety
- Full plan in local/docs/RELIBC-AGAINST-GLIBC-ASSESSMENT.md

Reference: glibc 2.41 cloned to local/reference/glibc/

Boot verified: greeter ready on VT 3 with refcounted semaphores

recipes/core/base/recipe.toml

@@ -3,7 +3,6 @@ git = "https://gitlab.redox-os.org/redox-os/base.git"
 rev = "463f76b9608a896e6f6c9f63457f57f6409873c7"
 patches = [
     "P0-daemon-fix-init-notify-unwrap.patch",
-    "P0-daemon-silence-init-notify.patch",
     "P0-workspace-add-bootstrap.patch",
     "P0-init-continuous-scheduling.patch",
 # TODO: P6-e1000d-msi-migration.patch conflicts with P6-driver-main-fixes