Add `e.source !== window` check to both content script and main-world
script message handlers, preventing iframes from injecting or
intercepting extension bridge messages.
Expose a serializable `systemInstruction` string field on the
page-facing ExecuteConfig, mapped to `instructions.system` when
creating MultiPageAgent. Functions cannot cross the postMessage
boundary, so this flat string field replaces the object form.
Closes#359
- add `stop` method. agent can be reused after stopped
- agent can not be reused after disposed
- extension DO NOT exposes `dispose` anymore. only `stop`.
- update panel for new `stop` method
- fix MultiPageAgent dispose event
- better handling abortSignal
Simon