feat(ui): app sessions overlay the current page in every display mode

Launching an app (or opening a tx in mempool from Home/wallet/channels) used
to router.push the app-session page in overlay/fullscreen modes, swapping the
page underneath — confusing and lossy. All display modes are now store-driven:
panel renders beside the page, overlay/fullscreen render above it (teleported
to body), and the route never changes. Deep-link paths (/tx/<hash>) ride along
via the launcher's panelPath instead of a route query; closing always returns
exactly where the user was. The app-session route stays for direct links.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/components/TransactionsModal.vue

@@ -75,9 +75,9 @@
 </template>
 
 <script setup lang="ts">
-import { useRouter } from 'vue-router'
 import { useI18n } from 'vue-i18n'
 import BaseModal from '@/components/BaseModal.vue'
+import { useAppLauncherStore } from '@/stores/appLauncher'
 
 interface WalletTransaction {
   tx_hash: string
@@ -100,7 +100,6 @@ defineProps<{
 
 const emit = defineEmits<{ close: [] }>()
 const { t } = useI18n()
-const router = useRouter()
 
 function close() {
   emit('close')
@@ -120,7 +119,8 @@ function kindLabel(tx: WalletTransaction): string {
 
 function openInMempool(tx: WalletTransaction) {
   if (!isOnchain(tx)) return
-  router.push({ name: 'app-session', params: { appId: 'mempool' }, query: { path: `/tx/${tx.tx_hash}` } })
+  // Overlay the explorer above the current page — never navigate away.
+  useAppLauncherStore().openSession('mempool', { path: `/tx/${tx.tx_hash}` })
 }
 
 function formatTxTime(timestamp: number): string {