feat(network): give the "no peers" banner an honest detail and a Restart action

The no-peers banner headline ("Connected, but no network peers") was followed
by a detail line that just repeated connection_status ("Connected"/"Peers: 0"),
reading as a contradiction, and it offered no action at the exact moment the
wallet looks synced but is silently stalled at a stale height.

- NoPeers now clears the passthrough detail; App renders a translated,
  actionable hint (node_banner_no_peers_detail) for this reason instead.
- When the embedded daemon is the node, offer a Restart button (re-triggers
  peer discovery via the -addnode seeds); an external node stays action-less
  since it is the user's own to restart.
- Update + extend the evaluator unit tests (external = no action/empty detail;
  embedded = RestartNode).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/node_status_banner.h

@@ -116,14 +116,20 @@ inline NodeBannerState evaluateNodeStatusBanner(const NodeBannerInputs& in) {
 
     // Connected to the daemon (RPC works) but with no peer-derived tip → the node has no peers and
     // cannot learn about new blocks; it silently stalls at a stale height while everything looks
-    // synced. Surface it as a recoverable warning (reconnect won't help, so no action button).
+    // synced. Surface it as a recoverable warning. A plain reconnect won't help, but restarting the
+    // embedded daemon re-triggers peer discovery (it re-reads the -addnode seeds), so offer that when
+    // we own the node; an external node is the user's own to restart, so no button there. The detail
+    // is left empty: here connection_status is just "Connected", which would contradict the
+    // "no peers" headline — App renders a translated, actionable hint for this reason instead.
     if (in.connected) {
         if (!in.tip_known && in.blocks > 0) {
             s.show     = true;
             s.severity = NodeBannerSeverity::Warning;
             s.reason   = NodeBannerReason::NoPeers;
-            s.action   = NodeBannerAction::None;
-            s.detail   = in.connection_status;
+            s.action   = (in.using_embedded_daemon && in.has_daemon_controller)
+                             ? NodeBannerAction::RestartNode
+                             : NodeBannerAction::None;
+            s.detail.clear();
         }
         return s;
     }