fix: include provider and model name in billing error message (#20510)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: 40dbdf62e8
Co-authored-by: echoVic <16428813+echoVic@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

src/agents/pi-embedded-subscribe.handlers.lifecycle.ts

@@ -35,6 +35,8 @@ export function handleAgentEnd(ctx: EmbeddedPiSubscribeContext) {
     const friendlyError = formatAssistantErrorText(lastAssistant, {
       cfg: ctx.params.config,
       sessionKey: ctx.params.sessionKey,
+      provider: lastAssistant.provider,
+      model: lastAssistant.model,
     });
     emitAgentEvent({
       runId: ctx.params.runId,