feat(nests): self highlight, floating reactions, kick drops p-tag, tap-self mute

#1 Local user's cell tints the username in colorScheme.primary so you
   can find yourself in a busy stage. Threads myPubkey through StageGrid
   and AudienceGrid; cells receive isSelf and pass MaterialTheme primary
   to UsernameDisplay's textColor.

#2 SpeakerReactionOverlay moves from below the username (which reflowed
   the column when reactions arrived and shoved neighbors down) to
   inside the avatar Box, anchored bottom-end with a small outward
   offset so it overlaps the corner without colliding with the
   bottom-center mic badge. Cell height stays constant whether the
   speaker has 0 or 5 active reactions.

#3 Kick now mirrors nostrnests' two-step path: the existing ephemeral
   kind-4312 ['action','kick'] kicks the target off the audio plane,
   followed by a re-published kind-30312 with their p-tag dropped so
   the participant grid stops rendering them. New
   RoomParticipantActions.removeParticipant builds the second event;
   refuses to drop the host (same protection as setRole demoting host).

#7 Tap-to-mute on your own avatar. Self-cell receives onTapSelf which,
   when broadcasting, toggles BroadcastUiState.Broadcasting.isMuted via
   the existing setMicMuted path. Falls back to no-op when not
   broadcasting so a non-broadcasting tap doesn't surface a useless
   action — the avatar simply isn't tappable.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/nests/room/participants/ParticipantHostActionsSheet.kt

@@ -302,7 +302,14 @@ internal fun ParticipantHostActionsSheet(
                     text = stringRes(R.string.nest_kick_action),
                     color = MaterialTheme.colorScheme.error,
                 ) {
+                    // Two-step kick mirroring nostrnests' ProfileCard.tsx:
+                    //   1. ephemeral kind-4312 ["action","kick"] kicks the
+                    //      user off the audio plane
+                    //   2. re-published kind-30312 with the target's p-tag
+                    //      dropped removes them from the participant grid
+                    //      so future presence events don't re-render them
                     broadcast(AdminCommandEvent.kick(roomATag, target))
+                    broadcast(RoomParticipantActions.removeParticipant(event, target))
                     onDismiss()
                 }
             }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/nests/room/participants/RoomParticipantActions.kt

@@ -90,6 +90,28 @@ internal object RoomParticipantActions {
         targetPubkey: String,
     ): EventTemplate<MeetingSpaceEvent>? = setRole(original, targetPubkey, ROLE.PARTICIPANT)
 
+    /**
+     * Drop [targetPubkey]'s p-tag from the room event entirely.
+     * Mirrors nostrnests' kick follow-up (`updateRoomParticipant(_,
+     * null)` after `kickUser` in `ProfileCard.tsx`): the kind-4312
+     * boots them off the audio plane, this re-published kind-30312
+     * keeps them out of the participant grid.
+     *
+     * Refuses to drop the host — same reasoning as [setRole]. Returns
+     * null if the target isn't currently in the participant list (a
+     * pure-audience kick has no list-mutation to do).
+     */
+    fun removeParticipant(
+        original: MeetingSpaceEvent,
+        targetPubkey: String,
+    ): EventTemplate<MeetingSpaceEvent>? {
+        val all = original.participants()
+        val target = all.firstOrNull { it.pubKey == targetPubkey } ?: return null
+        if (target.role.equals(ROLE.HOST.code, ignoreCase = true)) return null
+        val remaining = all.filterNot { it.pubKey == targetPubkey }
+        return rebuild(original, remaining, original.status() ?: StatusTag.STATUS.OPEN)
+    }
+
     private fun rebuild(
         original: MeetingSpaceEvent,
         participants: List<ParticipantTag>,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/nests/room/screen/NestFullScreen.kt

@@ -223,6 +223,14 @@ internal fun NestFullScreen(
                 summary = event.summary(),
                 listenerCount = presences.size,
             )
+            // Self-cell tap toggles mic-mute when broadcasting; null
+            // when not broadcasting so the avatar falls back to the
+            // default no-op tap (rather than offering a button that
+            // does nothing).
+            val onTapSelf: (() -> Unit)? =
+                (ui.broadcast as? com.vitorpamplona.amethyst.commons.viewmodels.BroadcastUiState.Broadcasting)?.let { state ->
+                    { viewModel.setMicMuted(!state.isMuted) }
+                }
             StageGrid(
                 members = participantGrid.onStage,
                 speakingNow = ui.speakingNow,
@@ -231,6 +239,8 @@ internal fun NestFullScreen(
                 reactionsByPubkey = reactionsByPubkey,
                 connectingSpeakers = ui.connectingSpeakers,
                 onLongPressParticipant = onLongPressParticipant,
+                myPubkey = myPubkey,
+                onTapSelf = onTapSelf,
                 modifier = Modifier.padding(horizontal = 16.dp),
             )
             NestTabRow(
@@ -258,6 +268,7 @@ internal fun NestFullScreen(
                         members = participantGrid.audience,
                         accountViewModel = accountViewModel,
                         onLongPressParticipant = onLongPressParticipant,
+                        myPubkey = myPubkey,
                         modifier =
                             Modifier
                                 .weight(1f)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/nests/room/stage/ParticipantsGrid.kt

@@ -119,6 +119,8 @@ internal fun StageGrid(
     reactionsByPubkey: Map<String, List<RoomReaction>> = emptyMap(),
     connectingSpeakers: ImmutableSet<String> = persistentSetOf(),
     onLongPressParticipant: ((String) -> Unit)? = null,
+    myPubkey: String? = null,
+    onTapSelf: (() -> Unit)? = null,
 ) {
     // Float currently-speaking members to the top so the listener can
     // see who they're hearing without scrolling. sortedBy is stable in
@@ -160,6 +162,7 @@ internal fun StageGrid(
             verticalArrangement = Arrangement.spacedBy(GRID_SPACING),
         ) {
             items(items = sortedMembers, key = { it.pubkey }) { member ->
+                val isSelf = myPubkey != null && member.pubkey == myPubkey
                 MemberCell(
                     member = member,
                     avatarSize = STAGE_AVATAR,
@@ -170,6 +173,8 @@ internal fun StageGrid(
                     reactions = reactionsByPubkey[member.pubkey].orEmpty(),
                     accountViewModel = accountViewModel,
                     onLongPressParticipant = onLongPressParticipant,
+                    isSelf = isSelf,
+                    onTapSelf = if (isSelf) onTapSelf else null,
                     modifier = Modifier.animateItem(),
                 )
             }
@@ -194,6 +199,7 @@ internal fun AudienceGrid(
     accountViewModel: AccountViewModel,
     modifier: Modifier = Modifier,
     onLongPressParticipant: ((String) -> Unit)? = null,
+    myPubkey: String? = null,
 ) {
     if (members.isEmpty()) {
         Box(
@@ -235,6 +241,7 @@ internal fun AudienceGrid(
                 reactions = emptyList(),
                 accountViewModel = accountViewModel,
                 onLongPressParticipant = onLongPressParticipant,
+                isSelf = myPubkey != null && member.pubkey == myPubkey,
                 modifier = Modifier.animateItem(),
             )
         }
@@ -252,6 +259,8 @@ private fun MemberCell(
     reactions: List<RoomReaction>,
     accountViewModel: AccountViewModel,
     onLongPressParticipant: ((String) -> Unit)?,
+    isSelf: Boolean = false,
+    onTapSelf: (() -> Unit)? = null,
     modifier: Modifier = Modifier,
 ) {
     val mutedRingColor = MaterialTheme.colorScheme.error
@@ -292,6 +301,17 @@ private fun MemberCell(
         remember(member.pubkey, onLongPressParticipant) {
             onLongPressParticipant?.let { cb -> { hex: String -> cb(hex) } }
         }
+    // Self-cell tap shortcut: tap your own avatar to toggle mic-mute
+    // when broadcasting. For other cells we leave tap unhandled so
+    // the existing nav-to-profile path stays consistent (and there's
+    // nothing visually different from a non-clickable avatar).
+    val onClick =
+        if (isSelf && onTapSelf != null) {
+            remember(onTapSelf) { { _: String -> onTapSelf() } }
+        } else {
+            null
+        }
+    val selfTint = if (isSelf) MaterialTheme.colorScheme.primary else Color.Unspecified
     Column(
         horizontalAlignment = Alignment.CenterHorizontally,
         modifier = modifier.fillMaxWidth().padding(vertical = 4.dp),
@@ -302,6 +322,7 @@ private fun MemberCell(
                 size = avatarSize,
                 accountViewModel = accountViewModel,
                 modifier = avatarModifier,
+                onClick = onClick,
                 onLongClick = onLongClick,
             )
             if (isConnecting) {
@@ -330,19 +351,27 @@ private fun MemberCell(
                     modifier = Modifier.align(Alignment.BottomCenter),
                 )
             }
+            // Reactions float over the avatar's bottom-right corner so
+            // a 👏 burst no longer pushes the username down and reflows
+            // neighbouring cells. The mic badge sits at BottomCenter,
+            // so BottomEnd + a small outward offset keeps them clear.
+            if (reactions.isNotEmpty()) {
+                SpeakerReactionOverlay(
+                    reactions = reactions,
+                    modifier =
+                        Modifier
+                            .align(Alignment.BottomEnd)
+                            .offset(x = 6.dp, y = 6.dp),
+                )
+            }
         }
         UsernameDisplay(
             baseUser = user,
             weight = Modifier.fillMaxWidth().padding(top = 4.dp),
+            textColor = selfTint,
             textAlign = TextAlign.Center,
             accountViewModel = accountViewModel,
         )
-        if (reactions.isNotEmpty()) {
-            SpeakerReactionOverlay(
-                reactions = reactions,
-                modifier = Modifier.padding(top = 2.dp),
-            )
-        }
     }
 }