relibc: full eventfd() implementation + no-stubs policy in AGENTS.md

Replaced P3-sys-eventfd-create.patch (constants-only stub) with:
- P3-eventfd-impl.patch: full eventfd() opening /scheme/event/eventfd
- P3-bits-eventfd.patch: eventfd_t type
- P3-eventfd-cbindgen.patch: generates sys/eventfd.h C header
- P3-bits-eventfd-mod.patch: wires bits_eventfd into header/mod.rs

libwayland: removed eventfd stub from redox.patch — relibc provides it now.
Only meson.build fix + wl_proxy null guards + MSG_NOSIGNAL guard remain.

Documented zero-tolerance stub policy at top of local/AGENTS.md.

recipes/core/relibc/P3-bits-eventfd-mod.patch

@@ -0,0 +1 @@
+../../../local/patches/relibc/P3-bits-eventfd-mod.patch

recipes/core/relibc/P3-bits-eventfd.patch

@@ -0,0 +1 @@
+../../../local/patches/relibc/P3-bits-eventfd.patch

recipes/core/relibc/P3-eventfd-cbindgen.patch

@@ -0,0 +1 @@
+../../../local/patches/relibc/P3-eventfd-cbindgen.patch

recipes/core/relibc/P3-eventfd-impl.patch

@@ -0,0 +1 @@
+../../../local/patches/relibc/P3-eventfd-impl.patch

recipes/core/relibc/recipe.toml

@@ -2,10 +2,15 @@
 git = "https://gitlab.redox-os.org/redox-os/relibc.git"
 rev = "861bbb0"
 patches = [
-    # Module declarations (pub mod sys_eventfd/signalfd/timerfd in header/mod.rs)
     "P3-eventfd-mod.patch",
-    # sys_eventfd module (constants only — libwayland has its own eventfd())
-    "P3-sys-eventfd-create.patch",
+    # Add pub mod bits_eventfd to header/mod.rs
+    "P3-bits-eventfd-mod.patch",
+    # bits_eventfd module (eventfd_t type)
+    "P3-bits-eventfd.patch",
+    # sys_eventfd module — FULL eventfd() implementation (opens /scheme/event/eventfd)
+    "P3-eventfd-impl.patch",
+    # cbindgen.toml for sys/eventfd.h C header generation
+    "P3-eventfd-cbindgen.patch",
     # sys_signalfd module (cbindgen.toml + mod.rs with cbindgen exports)
     "P3-signalfd-header.patch",
     # signalfd implementation (signal/signalfd.rs + signal/mod.rs wiring)