Add a unified observability interface for applications with multiple networks

include/kpn/static_network.hpp

@@ -110,14 +110,16 @@ public:
         for (auto* n : user_nodes_topo_)  n->start();
         for (auto* n : fanout_nodes_ptr_) n->start();
 #ifdef KPN_WEB_DEBUG
-        web_server_ = std::make_unique<web_debug::WebDebugServer>(
-            web_debug_port_,
-            [this]() {
-                auto s = collect_snapshots();
-                return web_debug::to_json(s.nodes, s.channels, s.resources, s.elapsed_s);
-            });
-        web_server_->start();
-        std::cerr << "[kpn] web debug UI: http://localhost:" << web_debug_port_ << "\n";
+        if (web_server_enabled_) {
+            web_server_ = std::make_unique<web_debug::WebDebugServer>(
+                web_debug_port_,
+                [this]() {
+                    auto s = collect_snapshots();
+                    return web_debug::to_json(s.nodes, s.channels, s.resources, s.elapsed_s);
+                });
+            web_server_->start();
+            std::cerr << "[kpn] web debug UI: http://localhost:" << web_debug_port_ << "\n";
+        }
 #endif
     }
 
@@ -142,8 +144,16 @@ public:
 
 #ifdef KPN_WEB_DEBUG
     void set_web_debug_port(uint16_t port) { web_debug_port_ = port; }
+    // Called by DebugHub::register_network() so the hub owns the debug server.
+    void disable_web_server() { web_server_enabled_ = false; }
 #endif
 
+    // Returns a snapshot of this network's nodes and channels for the DebugHub.
+    NetworkSnapshot network_snapshot() const {
+        auto s = collect_snapshots();
+        return {"", std::move(s.nodes), std::move(s.channels), s.elapsed_s};
+    }
+
     // Register a shared resource so it appears in diagnostics and the debug UI.
     // The probe must outlive this network (typically the resource is on the same stack).
     void register_resource(const std::string& name, IResourceProbe* probe) {
@@ -205,6 +215,7 @@ private:
     clock_t::time_point                                 start_time_;
 #ifdef KPN_WEB_DEBUG
     uint16_t                                            web_debug_port_{9090};
+    bool                                                web_server_enabled_{true};
     std::unique_ptr<web_debug::WebDebugServer>          web_server_;
 #endif
 };