fix(app): scope header overrides to gateway URLs only

- The session.webRequest.onHeadersReceived was stripping X-Frame-Options
  and modifying CSP for ALL responses including the Vite dev server,
  which could break the main app rendering. Now only applies to
  gateway URLs (127.0.0.1:18789 / localhost:18789).
- Dashboard: only fetch channels/skills when gateway is running
- Dashboard: guard against non-array channels/skills data
- Gateway store: use dynamic import() instead of require() for chat
  store to avoid ESM/CJS issues in Vite

src/stores/gateway.ts

@@ -62,13 +62,18 @@ export const useGatewayStore = create<GatewayState>((set, get) => ({
       
       // Listen for chat events from the gateway and forward to chat store
       window.electron.ipcRenderer.on('gateway:chat-message', (data) => {
-        const { useChatStore } = require('./chat');
-        const chatData = data as { message?: Record<string, unknown> } | Record<string, unknown>;
-        // The event payload may be nested under 'message' or directly on data
-        const event = ('message' in chatData && typeof chatData.message === 'object') 
-          ? chatData.message as Record<string, unknown>
-          : chatData as Record<string, unknown>;
-        useChatStore.getState().handleChatEvent(event);
+        try {
+          // Dynamic import to avoid circular dependency
+          import('./chat').then(({ useChatStore }) => {
+            const chatData = data as { message?: Record<string, unknown> } | Record<string, unknown>;
+            const event = ('message' in chatData && typeof chatData.message === 'object') 
+              ? chatData.message as Record<string, unknown>
+              : chatData as Record<string, unknown>;
+            useChatStore.getState().handleChatEvent(event);
+          });
+        } catch (err) {
+          console.warn('Failed to forward chat event:', err);
+        }
       });
       
     } catch (error) {