feat(ai): Add start event emission to all providers

- Emit start event with model and provider info after creating stream
- Add abort signal tests for all providers
- Update README abort signal section to reflect non-throwing API
- Fix model references in README examples

packages/ai/src/providers/google.ts

@@ -89,6 +89,14 @@ export class GoogleLLM implements LLM<GoogleLLMOptions> {
 				};
 			}
 
+			// Abort signal
+			if (options?.signal) {
+				if (options.signal.aborted) {
+					throw new Error("Request aborted");
+				}
+				config.abortSignal = options.signal;
+			}
+
 			// Build the request parameters
 			const params: GenerateContentParameters = {
 				model: this.model.id,
@@ -98,6 +106,8 @@ export class GoogleLLM implements LLM<GoogleLLMOptions> {
 
 			const stream = await this.client.models.generateContentStream(params);
 
+			options?.onEvent?.({ type: "start", model: this.model.id, provider: this.model.provider });
+
 			const blocks: AssistantMessage["content"] = [];
 			let currentBlock: TextContent | ThinkingContent | null = null;
 			let usage: Usage = {