Draw the focus indicator around the whole SelectedItem

Previously, only the small remove button could get the keyboard focus, and the
focus ring was barely visible. Now the whole item is focusable, the focus ring is
drawn around it, and pressing an activation key (Enter, Space, D-pad center)
removes the item. Touch behavior is unchanged: only the remove button is clickable.

Also add a shared `activationKeys` set in the designsystem module.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/components/SelectedItem.kt

@@ -9,6 +9,8 @@
 package io.element.android.libraries.matrix.ui.components
 
 import androidx.compose.foundation.clickable
+import androidx.compose.foundation.focusable
+import androidx.compose.foundation.indication
 import androidx.compose.foundation.interaction.MutableInteractionSource
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -25,11 +27,16 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.draw.clipToBounds
 import androidx.compose.ui.draw.drawWithContent
+import androidx.compose.ui.focus.focusProperties
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.BlendMode
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.CompositingStrategy
 import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.input.key.KeyEventType
+import androidx.compose.ui.input.key.key
+import androidx.compose.ui.input.key.onKeyEvent
+import androidx.compose.ui.input.key.type
 import androidx.compose.ui.platform.LocalLayoutDirection
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.semantics.clearAndSetSemantics
@@ -48,6 +55,7 @@ import io.element.android.libraries.designsystem.text.toPx
 import io.element.android.libraries.designsystem.theme.components.Icon
 import io.element.android.libraries.designsystem.theme.components.Surface
 import io.element.android.libraries.designsystem.theme.components.Text
+import io.element.android.libraries.designsystem.utils.activationKeys
 import io.element.android.libraries.ui.strings.CommonStrings
 
 @Composable
@@ -62,9 +70,31 @@ fun SelectedItem(
     modifier: Modifier = Modifier,
 ) {
     val actionRemove = stringResource(id = CommonStrings.action_remove)
+    val interactionSource = remember { MutableInteractionSource() }
     Box(
         modifier = modifier
             .width(avatarData.size.dp)
+            .then(
+                if (canRemove) {
+                    // Let the whole item get the keyboard focus, so that the focus indicator is drawn around it.
+                    Modifier
+                        .onKeyEvent { event ->
+                            if (event.type == KeyEventType.KeyUp && event.key in activationKeys) {
+                                onRemoveClick()
+                                true
+                            } else {
+                                false
+                            }
+                        }
+                        .indication(
+                            interactionSource = interactionSource,
+                            indication = ripple(),
+                        )
+                        .focusable(interactionSource = interactionSource)
+                } else {
+                    Modifier
+                }
+            )
             .clearAndSetSemantics {
                 contentDescription = a11yContentDescription
                 if (canRemove) {
@@ -130,6 +160,8 @@ fun SelectedItem(
                     .clip(CircleShape)
                     .size(20.dp)
                     .align(Alignment.TopEnd)
+                    // The whole item is focusable, not the remove button
+                    .focusProperties { canFocus = false }
                     .clickable(
                         indication = ripple(),
                         interactionSource = remember { MutableInteractionSource() },