feat: add kernel ACPI support for querying battery percentage, add battery indicator to desktop, move log state to 0:/state directory

programs/include/gui/desktop.hpp

@@ -217,6 +217,16 @@ struct DesktopState {
     uint64_t wifi_status_time;
 
 
+    // Battery indicator.  Absent entirely on a machine with no ACPI battery
+    // device, which is how a desktop keeps a clean panel.
+    SvgIcon icon_battery;
+    char battery_icon_name[64];            // which glyph icon_battery holds
+    bool battery_present;                  // a battery device exists
+    bool battery_popup_open;
+    Rect battery_icon_rect;
+    montauk::abi::BatteryInfo battery_info;
+    uint64_t battery_last_poll;
+
     bool vol_popup_open;
     Rect vol_icon_rect;
     int vol_level;            // 0-100