feat(a11y): Announce a low battery instead of only colouring it

Crossing the warn or critical threshold was expressed as a colour change only,
so it did not exist for a screen reader. Each battery slot on the overview card
now carries the level as a state description.

app/src/main/java/eu/darken/capod/main/ui/overview/cards/DualPodsCard.kt

@@ -50,6 +50,7 @@ import eu.darken.capod.monitor.core.visibleAncModes
 import eu.darken.capod.main.ui.overview.cards.components.AncModeSelector
 import eu.darken.capod.main.ui.overview.cards.components.BatteryCapsule
 import eu.darken.capod.main.ui.overview.cards.components.CompactBatterySummary
+import eu.darken.capod.main.ui.overview.cards.components.batteryTierState
 import eu.darken.capod.main.ui.overview.cards.components.DebugSection
 import eu.darken.capod.main.ui.overview.cards.components.DeviceConnectionBadge
 import eu.darken.capod.main.ui.overview.cards.components.MissingPairedDeviceBanner
@@ -330,7 +331,7 @@ private fun PodGauge(
     val ringColor = tier.fillColor()
 
     Column(
-        modifier = modifier,
+        modifier = modifier.batteryTierState(tier),
         horizontalAlignment = Alignment.CenterHorizontally,
     ) {
         // Ring with icon inside
@@ -420,7 +421,9 @@ private fun CaseRow(
 
     Row(
         verticalAlignment = Alignment.CenterVertically,
-        modifier = Modifier.fillMaxWidth(),
+        modifier = Modifier
+            .fillMaxWidth()
+            .batteryTierState(tier),
     ) {
         Image(
             painter = painterResource(device.caseIcon),

app/src/main/java/eu/darken/capod/main/ui/overview/cards/SinglePodsCard.kt

@@ -52,6 +52,7 @@ import eu.darken.capod.main.ui.overview.cards.components.DeviceConnectionBadge
 import eu.darken.capod.main.ui.overview.cards.components.MissingPairedDeviceBanner
 import eu.darken.capod.main.ui.overview.cards.components.SignalIndicator
 import eu.darken.capod.main.ui.overview.cards.components.StatusChip
+import eu.darken.capod.main.ui.overview.cards.components.batteryTierState
 import eu.darken.capod.common.SystemTimeSource
 import eu.darken.capod.common.compose.Preview2
 import eu.darken.capod.common.compose.PreviewWrapper
@@ -231,7 +232,9 @@ private fun ColumnScope.SinglePodsCardExpanded(
         ) {
             Box(
                 contentAlignment = Alignment.Center,
-                modifier = Modifier.size(88.dp),
+                modifier = Modifier
+                    .size(88.dp)
+                    .batteryTierState(tier),
             ) {
                 // Track ring
                 CircularProgressIndicator(

app/src/main/java/eu/darken/capod/main/ui/overview/cards/components/BatteryTierSemantics.kt

@@ -0,0 +1,23 @@
+package eu.darken.capod.main.ui.overview.cards.components
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.semantics.stateDescription
+import eu.darken.capod.R
+import eu.darken.capod.monitor.core.battery.BatteryTier
+
+/**
+ * Announces a low or critical level on a battery slot — crossing either threshold is otherwise
+ * only visible as a colour change. A no-op at the other tiers, which make no claim to announce.
+ */
+@Composable
+fun Modifier.batteryTierState(tier: BatteryTier): Modifier {
+    val description = when (tier) {
+        BatteryTier.CRITICAL -> stringResource(R.string.battery_state_critical_cd)
+        BatteryTier.WARN -> stringResource(R.string.battery_state_low_cd)
+        BatteryTier.UNKNOWN, BatteryTier.GOOD -> return this
+    }
+    return semantics(mergeDescendants = true) { stateDescription = description }
+}

app/src/main/java/eu/darken/capod/main/ui/overview/cards/components/CompactBatterySummary.kt

@@ -142,7 +142,7 @@ private fun MiniPodRing(
     val ringColor = tier.fillColor()
 
     Row(
-        modifier = modifier,
+        modifier = modifier.batteryTierState(tier),
         verticalAlignment = Alignment.CenterVertically,
     ) {
         Box(
@@ -197,7 +197,7 @@ private fun MiniCaseCluster(
     val tier = batteryTier(device.batteryCase)
 
     Row(
-        modifier = modifier,
+        modifier = modifier.batteryTierState(tier),
         verticalAlignment = Alignment.CenterVertically,
     ) {
         Image(

app/src/main/res/values/strings.xml

@@ -274,6 +274,8 @@
     <string name="pods_dual_right_short_label">R</string>
     <string name="pods_case_label">Case</string>
     <string name="battery_unavailable_label">Battery unavailable</string>
+    <string name="battery_state_low_cd">Battery low</string>
+    <string name="battery_state_critical_cd">Battery critically low</string>
     <string name="pods_case_status_open_label">Open</string>
     <string name="pods_case_status_closed_label">Closed</string>
     <string name="pods_connection_state_disconnected_label">Not connected to a device</string>