feat(toast): message toast opens the related chat + has a close icon (#33)

- Add a close (X) button to the message toast (closeToast, @click.stop) like the
  system notifications.
- Carry the sender pubkey on the toast; clicking now deep-links to that
  conversation (/dashboard/mesh?peer=<pubkey>) instead of the generic mesh page.
- Mesh.vue reads ?peer= on mount and opens the matching peer (by pubkey_hex/did),
  gracefully falling back to the mesh list when no match (B1/B2 identity).

type-check clean; useMessageToast tests 11/11.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

neode-ui/src/composables/useMessageToast.ts

@@ -14,7 +14,7 @@ const MESSAGE_POLL_INTERVAL = 30000 // 30s
 const receivedMessages = ref<ReceivedMessage[]>([])
 const lastMessageCount = ref(0)
 const loadingMessages = ref(false)
-const toastMessage = ref<{ show: boolean; text: string }>({ show: false, text: '' })
+const toastMessage = ref<{ show: boolean; text: string; fromPubkey: string }>({ show: false, text: '', fromPubkey: '' })
 let pollTimer: ReturnType<typeof setInterval> | null = null
 
 export function useMessageToast() {
@@ -37,6 +37,9 @@ export function useMessageToast() {
         toastMessage.value = {
           show: true,
           text: (newCount === 1 ? latest?.message : null) ?? `${newCount} new messages`,
+          // Only deep-link to a specific chat when it's a single new message
+          // from one sender; otherwise open the mesh list.
+          fromPubkey: newCount === 1 ? (latest?.from_pubkey ?? '') : '',
         }
         lastMessageCount.value = msgs.length
       } else {
@@ -83,9 +86,16 @@ export function useMessageToast() {
   }
 
   function dismissToastAndOpenMessages() {
-    toastMessage.value = { show: false, text: '' }
+    const peer = toastMessage.value.fromPubkey
+    toastMessage.value = { show: false, text: '', fromPubkey: '' }
     markAsRead()
-    router.push('/dashboard/mesh')
+    // Open the specific conversation when we know the sender; else the mesh list.
+    router.push(peer ? { path: '/dashboard/mesh', query: { peer } } : '/dashboard/mesh')
+  }
+
+  // Dismiss the toast without navigating (the close icon).
+  function closeToast() {
+    toastMessage.value = { show: false, text: '', fromPubkey: '' }
   }
 
   return {
@@ -99,5 +109,6 @@ export function useMessageToast() {
     stopPolling,
     markAsRead,
     dismissToastAndOpenMessages,
+    closeToast,
   }
 }