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

programs/src/power/main.cpp

@@ -95,6 +95,63 @@ static void print_snapshot(const montauk::abi::PowerInfo& info) {
     print("\n");
 }
 
+// Battery is reported independently of the CPU power features: a laptop under
+// emulation has neither, but a real one may well expose a battery and no HWP.
+static void print_battery() {
+    montauk::abi::BatteryInfo b{};
+    if (montauk::battery_info(&b) != 0) {
+        print("Battery:      none (no ACPI battery device)\n");
+        return;
+    }
+
+    if (!b.present) {
+        print("Battery:      slot present, no pack installed");
+        if (b.hasAcAdapter) print(b.acOnline ? " (on AC)" : " (no AC)");
+        print("\n");
+        return;
+    }
+
+    print("Battery:      ");
+    put_u64(b.percent);
+    print("%");
+
+    if (b.charging)         print(", charging");
+    else if (b.acOnline)    print(", on AC, not charging");
+    else                    print(", discharging");
+    if (b.critical)         print(", CRITICAL");
+    print("\n");
+
+    if (b.fullCapacity > 0) {
+        print("  Capacity:   ");
+        put_u64(b.remainingCapacity);
+        print(" of ");
+        put_u64(b.fullCapacity);
+        print(b.powerUnitMilliAmps ? " mAh (design " : " mWh (design ");
+        put_u64(b.designCapacity);
+        print(")\n");
+    }
+
+    if (b.presentRate > 0) {
+        print("  Rate:       ");
+        put_u64(b.presentRate);
+        print(b.powerUnitMilliAmps ? " mA\n" : " mW\n");
+    }
+
+    if (b.minutesRemaining >= 0) {
+        print("  Time left:  ");
+        put_u64((uint64_t)(b.minutesRemaining / 60));
+        print("h ");
+        put_u64((uint64_t)(b.minutesRemaining % 60));
+        print("m\n");
+    }
+
+    if (b.voltageMv > 0) {
+        print("  Voltage:    ");
+        put_u64(b.voltageMv);
+        print(" mV\n");
+    }
+}
+
 static void print_watch_line(const montauk::abi::PowerInfo& info, uint64_t t) {
     put_u64(t);
     print("s  ");
@@ -124,13 +181,16 @@ extern "C" void _start() {
     montauk::abi::PowerInfo info{};
     if (!read_info(info)) {
         print("power: no CPU power management available\n");
-        print("(non-Intel CPU or running under emulation)\n");
+        print("(non-Intel CPU or running under emulation)\n\n");
+        print_battery();
         montauk::exit(1);
     }
 
     bool watch = rest[0] == 'w';
     if (!watch) {
         print_snapshot(info);
+        print("\n");
+        print_battery();
         montauk::exit(0);
     }