power: proper shutdown via UEFI ResetSystem (ACPI S5)

- uefi.rs: full EFI_RUNTIME_SERVICES layout with reset_system at index 10
  (spec order); EfiResetSystem type + RESET_* constants
- power.rs: stash the runtime-services table pre-EBS; poweroff() calls
  ResetSystem(EfiResetShutdown) — still callable after ExitBootServices
  because we never call SetVirtualAddressMap, so the pointers keep
  working with physical addresses; falls back to the hlt loop
- shell: 'poweroff' and 'exit' shut the machine down (QEMU exits),
  'halt' keeps the plain hlt loop

1 files changed, 3 insertions, 0 deletions

diff --git a/rsdos/src/main.rs b/rsdos/src/main.rs
index 1169785..d9578e2 100644
--- a/rsdos/src/main.rs
+++ b/rsdos/src/main.rs
@@ -37,6 +37,9 @@ pub extern "efiapi" fn efi_main(image_handle: Handle, system_table: *mut SystemT
     let bs = unsafe { &mut *st.boot_services };
     let con_out = unsafe { &mut *st.con_out };
 
+    // Keep the runtime-services table for later (ResetSystem → poweroff).
+    rsnix::power::init(st.runtime_services);
+
     // ---- Phase 1: UEFI boot services alive ----
 
     // Print banner via UEFI console