Add lifecycle callbacks to SandboxRuntimeProvider for abort signal support

- Added onExecutionStart(sandboxId, signal) - called when sandbox execution begins
- Added onExecutionEnd(sandboxId) - called when sandbox execution ends
- Integrated callbacks in SandboxedIframe.execute()
- Enables providers to track and cancel async operations (e.g., userScript executions)

packages/web-ui/src/components/SandboxedIframe.ts

@@ -254,6 +254,11 @@ export class SandboxIframe extends LitElement {
 		providers = [consoleProvider, ...providers];
 		RUNTIME_MESSAGE_ROUTER.registerSandbox(sandboxId, providers, consumers);
 
+		// Notify providers that execution is starting
+		for (const provider of providers) {
+			provider.onExecutionStart?.(sandboxId, signal);
+		}
+
 		const files: SandboxFile[] = [];
 		let completed = false;
 
@@ -287,6 +292,11 @@ export class SandboxIframe extends LitElement {
 			RUNTIME_MESSAGE_ROUTER.addConsumer(sandboxId, executionConsumer);
 
 			const cleanup = () => {
+				// Notify providers that execution has ended
+				for (const provider of providers) {
+					provider.onExecutionEnd?.(sandboxId);
+				}
+
 				RUNTIME_MESSAGE_ROUTER.unregisterSandbox(sandboxId);
 				signal?.removeEventListener("abort", abortHandler);
 				clearTimeout(timeoutId);

packages/web-ui/src/components/sandbox/SandboxRuntimeProvider.ts

@@ -32,4 +32,21 @@ export interface SandboxRuntimeProvider {
 	 * This will be appended to tool descriptions dynamically so the LLM knows what's available.
 	 */
 	getDescription(): string;
+
+	/**
+	 * Optional lifecycle callback invoked when sandbox execution starts.
+	 * Providers can use this to track abort signals for cancellation of async operations.
+	 *
+	 * @param sandboxId - The unique identifier for this sandbox execution
+	 * @param signal - Optional AbortSignal that will be triggered if execution is cancelled
+	 */
+	onExecutionStart?(sandboxId: string, signal?: AbortSignal): void;
+
+	/**
+	 * Optional lifecycle callback invoked when sandbox execution ends (success, error, or abort).
+	 * Providers can use this to clean up any resources associated with the sandbox.
+	 *
+	 * @param sandboxId - The unique identifier for this sandbox execution
+	 */
+	onExecutionEnd?(sandboxId: string): void;
 }