fix(kernel-browser-runtime): snapshot map keys before iteration in terminateAll

Use Array.from() to snapshot uiVats keys before iterating, consistent
with the pattern in PlatformServicesServer.ts. Prevents potential issues
from map modification during iteration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sirtimid

packages/kernel-browser-runtime/src/ui/UIOrchestrator.ts

@@ -205,7 +205,7 @@ export class UIOrchestrator {
    */
   terminateAll(): void {
     this.#logger.info('Terminating all UI vats');
-    for (const id of this.#uiVats.keys()) {
+    for (const id of Array.from(this.#uiVats.keys())) {
       this.terminate(id);
     }
   }