fix(frontend): initializeStores dedup + retryAllMessages guard + as any cleanup

- index.ts: add _storesInitialized guard to prevent triple initialization
- offlineStore.ts: add isRetrying mutex for retryAllMessages concurrency
- PropertyPanel.tsx: replace 13x (data as any) with typed d accessor
- chatStore.ts: replace window as any with Record<string, unknown>
- kernel-*.ts: replace prototype as any with Record<string, unknown>
- gateway-heartbeat.ts: delete dead code (9 as any, zero imports)

desktop/src/lib/kernel-chat.ts

@@ -13,7 +13,7 @@ import type { ChatResponse, StreamCallbacks, StreamChunkPayload } from './kernel
 const log = createLogger('KernelClient');
 
 export function installChatMethods(ClientClass: { prototype: KernelClient }): void {
-  const proto = ClientClass.prototype as any;
+  const proto = ClientClass.prototype as unknown as Record<string, unknown>;
 
   /**
    * Send a message and get a response
@@ -227,13 +227,13 @@ export function installChatMethods(ClientClass: { prototype: KernelClient }): vo
    * Set default agent ID
    */
   proto.setDefaultAgentId = function (this: KernelClient, agentId: string): void {
-    (this as any).defaultAgentId = agentId;
+    this.defaultAgentId = agentId;
   };
 
   /**
    * Get default agent ID
    */
   proto.getDefaultAgentId = function (this: KernelClient): string {
-    return (this as any).defaultAgentId || '';
+    return this.defaultAgentId || '';
   };
 }