fix: simplify macOS sleep inhibitor FFI (#12340)

Summary
- simplify the macOS sleep inhibitor FFI by replacing `dlopen` / `dlsym`
/ `transmute` with normal IOKit extern calls and `SAFETY` comments
- switch to cfg-selected platform implementations
(`imp::SleepInhibitor`) instead of `Box<dyn ...>`
- check in minimal IOKit bindings generated with `bindgen` and include
them from the macOS backend
- enable direct IOKit linkage in Bazel macOS builds by registering
`IOKit` in the Bazel `osx.framework(...)` toolchain extension list
- update `Cargo.lock` and `MODULE.bazel.lock` after removing the
build-time `bindgen` dependency path

Testing
- `just fmt`
- `cargo clippy -p codex-utils-sleep-inhibitor --all-targets -- -D
warnings`
- `cargo test -p codex-utils-sleep-inhibitor`
- `bazel test //codex-rs/utils/sleep-inhibitor:all --test_output=errors`
- `just bazel-lock-update`
- `just bazel-lock-check`

Context
- follow-up to #11711 addressing Ryan's review comments
- `bindgen` is used to generate the checked-in bindings file, but not at
build time

codex-rs/utils/sleep-inhibitor/src/iokit_bindings.rs

@@ -0,0 +1,27 @@
+/* automatically generated by rust-bindgen 0.71.1 */
+
+pub const kIOReturnSuccess: u32 = 0;
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct __CFString {
+    _unused: [u8; 0],
+}
+pub type CFStringRef = *const __CFString;
+pub type kern_return_t = ::std::os::raw::c_int;
+pub type IOReturn = kern_return_t;
+pub type IOPMAssertionID = u32;
+pub type IOPMAssertionLevel = u32;
+pub const kIOPMAssertionLevelOff: _bindgen_ty_36 = 0;
+pub const kIOPMAssertionLevelOn: _bindgen_ty_36 = 255;
+pub type _bindgen_ty_36 = ::std::os::raw::c_uint;
+unsafe extern "C" {
+    pub fn IOPMAssertionRelease(AssertionID: IOPMAssertionID) -> IOReturn;
+}
+unsafe extern "C" {
+    pub fn IOPMAssertionCreateWithName(
+        AssertionType: CFStringRef,
+        AssertionLevel: IOPMAssertionLevel,
+        AssertionName: CFStringRef,
+        AssertionID: *mut IOPMAssertionID,
+    ) -> IOReturn;
+}