fix(desktop): fix NWC relay connection, disconnect crash, and balance error handling

- Remove premature ensureRelayConnected check — NostrClient connects
  on subscribe/publish via sendOrConnectAndSync
- Fix disconnect crash: use appScope instead of rememberCoroutineScope
  to survive recomposition when nwcConnection goes null
- Surface balance errors/timeouts as snackbars instead of silent swallow
- Add ensureRelayConnected helper to RelayConnectionManager
- Add Phase 2 embedded wallet research doc

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

desktopApp/plans/2026-05-21-embedded-wallet-phase2-research.md

@@ -0,0 +1,50 @@
+# Phase 2: Embedded Self-Custodial Wallet — Research Summary
+
+**Date:** 2026-05-21
+**Status:** Research complete, parked. Return after NWC parity (Phase 1) ships.
+
+## Context
+
+No desktop Nostr client has an embedded wallet. All use NWC. This would be a first.
+
+## Top Candidates (High Sovereignty)
+
+| | Breez SDK Spark | ldk-node-jvm | lightning-kmp |
+|---|---|---|---|
+| Sovereignty | Full | Full | Full |
+| Architecture | No channels | Channels + LSPS2 | Single channel + splicing |
+| KMP/JVM | KMP artifact (`breez-sdk-spark-kmp:0.7.10`) | JVM JAR (`ldk-node-jvm:0.7.0`) | KMP (`lightning-kmp:1.8.4`) |
+| LSP lock-in | None | Any LSPS2 | ACINQ only |
+| Embedding docs | Breez docs | Good | None |
+| License | MIT | MIT/Apache-2.0 | Apache-2.0 |
+
+### Recommended path
+
+1. **Spike Breez SDK Spark** — verify KMP artifact works on JVM desktop (not just Android)
+2. **Fallback: ldk-node-jvm** — proven JVM, any LSP, well-documented
+3. **Skip: lightning-kmp** — ACINQ LSP lock-in, no embedding docs
+
+### Eliminated
+
+- phoenixd: subprocess, no Windows native
+- Breez SDK Liquid: Android-only bindings
+- Greenlight: weak JVM support
+- Cashu: not self-custodial (mint trust)
+
+## Open Questions
+
+1. Does `breez-sdk-spark-kmp` include JVM desktop native libs?
+2. Spark fee economics for small zaps (10-100 sats)?
+3. Does `ldk-node-jvm` bundle macOS arm64/x64 + Linux x64 natives?
+4. Which LSPS2 LSPs are publicly available?
+5. Would ACINQ accept third-party lightning-kmp clients?
+
+## Nostr App Landscape
+
+| App | Wallet | Type |
+|-----|--------|------|
+| Primal | Strike (custodial), maybe migrating to Spark | Built-in |
+| 0xchat | cashu-dart | Cashu ecash |
+| YakiHonne | Cashu + NWC | Dual |
+| Amethyst Android | NWC + Cashu token parsing | External |
+| All desktop clients | NWC only | External |

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/network/RelayConnectionManager.kt

@@ -144,6 +144,26 @@ open class RelayConnectionManager(
         publish(event, connected)
     }
 
+    /**
+     * Waits for a relay to appear in connectedRelays, adding it if needed.
+     * Returns true if connected within the timeout, false otherwise.
+     */
+    suspend fun ensureRelayConnected(
+        relay: NormalizedRelayUrl,
+        timeoutMs: Long = 10_000,
+    ): Boolean {
+        if (relay in connectedRelays.value) return true
+        if (relay !in availableRelays.value) {
+            updateRelayStatus(relay) { it.copy(connected = false, error = null) }
+        }
+        val deadline = System.currentTimeMillis() + timeoutMs
+        while (System.currentTimeMillis() < deadline) {
+            if (relay in connectedRelays.value) return true
+            delay(200)
+        }
+        return relay in connectedRelays.value
+    }
+
     /**
      * Sends an event to a specific relay (for NWC).
      * Adds the relay if not already in the list.

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/nwc/NwcPaymentHandler.kt

@@ -209,17 +209,19 @@ class NwcPaymentHandler(
         timeoutMs: Long = 30_000,
     ): BalanceResult {
         val secret = nwcConnection.secret ?: return BalanceResult.Error("NWC connection has no secret")
+
         val nwcSigner = NostrSignerInternal(KeyPair(secret.hexToByteArray()))
         val client = Nip47Client.fromNip47URI(nwcConnection)
         val requestEvent = client.getBalance()
 
         return withTimeoutOrNull(timeoutMs) {
-            // Subscribe BEFORE publishing to avoid race with fast wallet responses
             waitForGenericResponse(
                 requestId = requestEvent.id,
                 nwcConnection = nwcConnection,
                 nwcSigner = nwcSigner,
-                onSubscribed = { relayManager.publishToRelay(nwcConnection.relayUri, requestEvent) },
+                onSubscribed = {
+                    relayManager.publishToRelay(nwcConnection.relayUri, requestEvent)
+                },
             ) { response ->
                 when (response) {
                     is GetBalanceSuccessResponse -> {
@@ -261,6 +263,7 @@ class NwcPaymentHandler(
         timeoutMs: Long = 30_000,
     ): InvoiceResult {
         val secret = nwcConnection.secret ?: return InvoiceResult.Error("NWC connection has no secret")
+
         val nwcSigner = NostrSignerInternal(KeyPair(secret.hexToByteArray()))
         val client = Nip47Client.fromNip47URI(nwcConnection)
         val requestEvent = client.makeInvoice(amountMsats, description)
@@ -319,6 +322,7 @@ class NwcPaymentHandler(
                 subId = subId,
                 filters = listOf(filter),
                 onEvent = { event, _ ->
+                    println("NWC rpc event received: kind=${event.kind} id=${event.id.take(8)} from=${event.pubKey.take(8)}")
                     if (event is LnZapPaymentResponseEvent && event.requestId() == requestId) {
                         @OptIn(kotlinx.coroutines.DelicateCoroutinesApi::class)
                         kotlinx.coroutines.GlobalScope.launch(kotlinx.coroutines.Dispatchers.IO) {

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/wallet/WalletColumnScreen.kt

@@ -112,7 +112,15 @@ fun WalletColumnScreen(
                     balanceSats = result.balanceMsats / 1000
                 }
 
-                else -> {}
+                is NwcPaymentHandler.BalanceResult.Error -> {
+                    println("NWC balance error: ${result.message}")
+                    snackbarHostState.showSnackbar("Balance error: ${result.message}")
+                }
+
+                is NwcPaymentHandler.BalanceResult.Timeout -> {
+                    println("NWC balance timeout")
+                    snackbarHostState.showSnackbar("Balance request timed out")
+                }
             }
             isLoadingBalance = false
         }
@@ -204,10 +212,9 @@ fun WalletColumnScreen(
                     )
 
                     TextButton(onClick = {
-                        scope.launch {
+                        appScope.launch {
                             accountManager.clearNwcConnection(account.npub)
                             balanceSats = null
-                            snackbarHostState.showSnackbar("Wallet disconnected")
                         }
                     }) {
                         Text("Disconnect", color = MaterialTheme.colorScheme.error)