feat(multi-account): add account switcher dropdown in sidebar

Phase 4: account switcher UI.

- AccountSwitcherDropdown composable (person icon → dropdown menu)
- Shows all accounts with active checkmark and signer type label
- "Add Account" button at bottom with divider
- DropdownMenu with DpOffset(48dp) to expand right of sidebar
- DeckSidebar now takes account params (activeNpub, allAccounts, callbacks)
- Replaces "A" logo text with account switcher button
- Migration called on startup to populate account list
- Account switch wired through to AccountManager.switchAccount()

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/Main.kt

@@ -198,6 +198,7 @@ fun main() {
         val workspaceManager = remember { WorkspaceManager(deckScope).also { it.load() } }
         val accountManager = remember { AccountManager.create() }
         val accountState by accountManager.accountState.collectAsState()
+        val allAccounts by accountManager.allAccounts.collectAsState()
         var showAppDrawer by remember { mutableStateOf(false) }
 
         // Tor state at Window level — survives key() app rebuild
@@ -663,6 +664,9 @@ fun App(
         subscriptionsCoordinator.start()
 
         scope.launch(Dispatchers.IO) {
+            // Migrate legacy single-account files and load account list
+            accountManager.migrateAndLoadAccounts()
+
             if (accountManager.hasBunkerAccount()) {
                 // Show connecting UI while dedicated NIP-46 client connects
                 accountManager.setConnectingRelays()
@@ -1016,7 +1020,18 @@ fun MainContent(
 
                     LayoutMode.DECK -> {
                         if (!isImmersive) {
+                            val allAccountsState by accountManager.allAccounts.collectAsState()
                             DeckSidebar(
+                                activeNpub = accountManager.currentAccount()?.npub,
+                                allAccounts = allAccountsState,
+                                onSwitchAccount = { npub ->
+                                    scope.launch(Dispatchers.IO) {
+                                        accountManager.switchAccount(npub)
+                                    }
+                                },
+                                onAddAccount = {
+                                    // TODO: Show add account dialog
+                                },
                                 onAddColumn = onShowAppDrawer,
                                 onOpenSettings = {
                                     if (deckState.hasColumnOfType(DeckColumnType.Settings)) {

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/account/AccountSwitcherDropdown.kt

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.desktop.ui.account
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.size
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Add
+import androidx.compose.material.icons.filled.Check
+import androidx.compose.material.icons.filled.Person
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.DpOffset
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.commons.model.account.AccountInfo
+import com.vitorpamplona.amethyst.commons.model.account.SignerType
+import kotlinx.collections.immutable.ImmutableList
+
+@Composable
+fun AccountSwitcherDropdown(
+    activeNpub: String?,
+    allAccounts: ImmutableList<AccountInfo>,
+    onSwitchAccount: (String) -> Unit,
+    onAddAccount: () -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    var expanded by remember { mutableStateOf(false) }
+
+    Box(modifier = modifier) {
+        IconButton(
+            onClick = { expanded = true },
+            modifier = Modifier.size(48.dp),
+        ) {
+            Icon(
+                Icons.Default.Person,
+                contentDescription = "Switch account",
+                tint = MaterialTheme.colorScheme.primary,
+            )
+        }
+
+        DropdownMenu(
+            expanded = expanded,
+            onDismissRequest = { expanded = false },
+            offset = DpOffset(x = 48.dp, y = 0.dp),
+        ) {
+            if (allAccounts.isEmpty()) {
+                DropdownMenuItem(
+                    text = { Text("No accounts") },
+                    onClick = {},
+                    enabled = false,
+                )
+            } else {
+                allAccounts.forEach { account ->
+                    val isActive = account.npub == activeNpub
+                    DropdownMenuItem(
+                        text = {
+                            Column {
+                                Text(
+                                    account.npub.take(16) + "...",
+                                    maxLines = 1,
+                                    overflow = TextOverflow.Ellipsis,
+                                    fontWeight = if (isActive) FontWeight.SemiBold else FontWeight.Normal,
+                                )
+                                val label =
+                                    when (account.signerType) {
+                                        is SignerType.Remote -> "Bunker"
+                                        is SignerType.ViewOnly -> "View only"
+                                        is SignerType.Internal -> null
+                                    }
+                                if (label != null) {
+                                    Text(
+                                        label,
+                                        style = MaterialTheme.typography.labelSmall,
+                                        color = MaterialTheme.colorScheme.primary,
+                                    )
+                                }
+                            }
+                        },
+                        trailingIcon = {
+                            if (isActive) {
+                                Icon(
+                                    Icons.Default.Check,
+                                    contentDescription = "Active",
+                                    tint = MaterialTheme.colorScheme.primary,
+                                )
+                            }
+                        },
+                        onClick = {
+                            expanded = false
+                            if (!isActive) onSwitchAccount(account.npub)
+                        },
+                    )
+                }
+            }
+            HorizontalDivider()
+            DropdownMenuItem(
+                text = { Text("Add Account") },
+                leadingIcon = { Icon(Icons.Default.Add, contentDescription = null) },
+                onClick = {
+                    expanded = false
+                    onAddAccount()
+                },
+            )
+        }
+    }
+}

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/deck/DeckSidebar.kt

@@ -34,20 +34,24 @@ import androidx.compose.material.icons.filled.Settings
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
-import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
-import androidx.compose.ui.unit.sp
 import com.vitorpamplona.amethyst.commons.domain.nip46.SignerConnectionState
+import com.vitorpamplona.amethyst.commons.model.account.AccountInfo
 import com.vitorpamplona.amethyst.commons.tor.TorServiceStatus
 import com.vitorpamplona.amethyst.commons.ui.components.BunkerHeartbeatIndicator
+import com.vitorpamplona.amethyst.desktop.ui.account.AccountSwitcherDropdown
 import com.vitorpamplona.amethyst.desktop.ui.tor.TorStatusIndicator
+import kotlinx.collections.immutable.ImmutableList
 
 @Composable
 fun DeckSidebar(
+    activeNpub: String?,
+    allAccounts: ImmutableList<AccountInfo>,
+    onSwitchAccount: (String) -> Unit,
+    onAddAccount: () -> Unit,
     onAddColumn: () -> Unit,
     onOpenSettings: () -> Unit,
     signerConnectionState: SignerConnectionState,
@@ -65,12 +69,11 @@ fun DeckSidebar(
         horizontalAlignment = Alignment.CenterHorizontally,
         verticalArrangement = Arrangement.Top,
     ) {
-        Text(
+        AccountSwitcherDropdown(
-            "A",
+            activeNpub = activeNpub,
-            style = MaterialTheme.typography.titleLarge,
+            allAccounts = allAccounts,
-            fontWeight = FontWeight.Bold,
+            onSwitchAccount = onSwitchAccount,
-            color = MaterialTheme.colorScheme.primary,
+            onAddAccount = onAddAccount,
-            fontSize = 20.sp,
         )
 
         Spacer(Modifier.size(16.dp))