syscall: add AcpiVerb::SetS3WakingVector and AcpiVerb::EnterS3 (Phase II.X.W)

Phase II.X.W: extend the AcpiVerb enum with two new variants
for the S3 round-trip:

* AcpiVerb::SetS3WakingVector (= 5): acpid writes the
  kernel's S3 resume trampoline address to FACS.
  Mirrors Linux 7.1's acpi_set_firmware_waking_vector.
  The 8-byte write payload is the address in
  little-endian. A zero payload is a sentinel for 'use the
  kernel's default trampoline address' (s3_trampoline
  symbol).
* AcpiVerb::EnterS3 (= 6): acpid requests the kernel to
  enter S3. The kernel's stop::enter_s3() reads the
  SLP_TYP value from S3_SLP_TYP and does the PM1 register
  write. The actual S3 entry happens via acpid writing
  to /scheme/sys/kstop.

Hardware-agnostic: works on any x86_64 system with
standard ACPI S3 support (Dell, HP, Lenovo, LG Gram 14).
On Modern Standby-only systems (LG Gram 16 (2025)), the
kernel never enters S3 so these verbs are no-ops.

src/flag.rs

@@ -325,6 +325,28 @@ pub enum AcpiVerb {
     /// byte) always returns 0. Mirrors Linux 7.1 `s2idle_wake()` in
     /// `kernel/power/suspend.c:133`. Hardware-agnostic.
     ExitS2Idle = 4,
+    /// Red Bear OS extension (Phase II.X.W): acpid writes the
+    /// 64-bit kernel S3 resume trampoline address to
+    /// FACS.xfirmware_waking_vector. The kernel's
+    /// `arch/x86_shared/s3_resume.rs` trampoline is at this
+    /// address; the platform firmware jumps to it on S3 wake.
+    /// Write payload: 8-byte little-endian u64 (the trampoline
+    /// address). Read payload: 0 (no error condition; this verb
+    /// is one-way). Mirrors Linux 7.1's
+    /// `acpi_set_firmware_waking_vector` in ACPICA.
+    /// Hardware-agnostic: works on any x86_64 system with
+    /// standard ACPI S3 support (Dell, HP, Lenovo, LG Gram 14).
+    SetS3WakingVector = 5,
+    /// Red Bear OS extension (Phase II.X.W): acpid requests
+    /// the kernel to enter S3. The kernel's kstop handler
+    /// dispatches on the "s3" string arg, dispatches on the
+    /// SLP_TYP byte, and does the PM1 register write. The
+    /// acpid has already done the AML prep (`_TTS(3)`, `_PTS(3)`,
+    /// `_SST(3)`) and written the trampoline address to FACS
+    /// via `SetS3WakingVector`. No payload needed.
+    /// Mirrors Linux 7.1's `enter_sleep_state` /
+    /// `acpi_hw_legacy_sleep` for S3.
+    EnterS3 = 6,
 }
 impl AcpiVerb {
     pub const fn try_from_raw(value: u64) -> Option<Self> {
@@ -333,6 +355,8 @@ impl AcpiVerb {
             2 => Self::CheckShutdown,
             3 => Self::EnterS2Idle,
             4 => Self::ExitS2Idle,
+            5 => Self::SetS3WakingVector,
+            6 => Self::EnterS3,
             _ => return None,
         })
     }