feat: disconnect Bluetooth devices, flush disks on shutdown/reboot, display progress in login.elf window

programs/include/Api/Syscall.hpp

@@ -173,6 +173,21 @@ namespace Montauk {
     static constexpr uint64_t SYS_THREAD_JOIN         = 132;
     static constexpr uint64_t SYS_THREAD_SELF         = 133;
 
+    // Flush + unmount persistent volumes for power-off
+    static constexpr uint64_t SYS_FS_SYNC             = 134;
+
+    // Cross-process graceful power-off request channel
+    static constexpr uint64_t SYS_POWER_REQUEST       = 135;
+
+    // Graceful power-off request actions (SYS_POWER_REQUEST). The desktop posts
+    // a pending action and exits; login.elf reads it, runs the shutdown stages,
+    // then issues the matching SYS_SHUTDOWN / SYS_RESET.
+    enum PowerRequestAction : int {
+        POWER_REQ_QUERY    = 0,  // read-and-clear the pending action
+        POWER_REQ_SHUTDOWN = 1,
+        POWER_REQ_REBOOT   = 2,
+    };
+
     static constexpr uint32_t CLIPBOARD_MAX_TEXT_BYTES = 256 * 1024;
 
     static constexpr uint32_t IPC_SIGNAL_READABLE    = 1u << 0;