test(sweep): capture the no-peers node banner on its full-node sweep target

renderNodeStatusBanner suppresses itself during a UI sweep (the forced demo
state would otherwise paint a banner over every tab). Add a narrow opt-in
(sweep_show_node_banner_) so ONLY the overview-no-peers target shows it; every
other capture is unchanged. The target also clears connection_in_progress_ so
the evaluator classifies the state as no-peers rather than "connecting".

Verified in a full-node + DRAGONX_ENABLE_UI_SWEEP build: the banner renders as
"Connected, but no network peers — the node can't sync · Check your internet
connection and firewall, then restart the node to find peers." (Restart button
only appears with an embedded daemon, which the sweep has none of.)

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

src/app.h

@@ -1676,6 +1676,7 @@ private:
     // The full sweep's private temp dir (demo wallet files and folders); "" when none.
     std::string sweep_sandbox_;
     bool sweep_chat_identity_fabricated_ = false;   // seedChatDemoData() made the demo chat identity
+    bool sweep_show_node_banner_ = false;           // let the node-status banner render on its sweep target
     void applyHealthyDemoState();  // reset the connection/encryption flags to the healthy demo values
     void sweepEnsureDemoChatIdentity();  // re-fabricate a demo chat identity if none (sweep teardown)
     void writeSweepManifest() const;