test: add PI release proof harness

scripts/probe-pi-runtime.mjs

@@ -857,9 +857,16 @@ async function promptAndSettle(worker, message, images, timeoutMs) {
     (event) => worker.events.indexOf(event) >= eventStartIndex && event.type === 'agent_settled',
     timeoutMs,
   );
+  const firstProviderEvent = worker.events
+    .slice(eventStartIndex)
+    .find((event) => event !== agentStart && event.receivedAt >= agentStart.receivedAt);
   const messagesResponse = await worker.request({ type: 'get_messages' });
   return {
     acceptedMs: accepted.receivedAt - sentAt,
+    agentStartMs: agentStart.receivedAt - accepted.receivedAt,
+    providerFirstEventMs: firstProviderEvent
+      ? firstProviderEvent.receivedAt - agentStart.receivedAt
+      : settled.receivedAt - agentStart.receivedAt,
     startedAt: agentStart.receivedAt,
     settledAt: settled.receivedAt,
     stopReason: lastAssistantStopReason(messagesResponse),
@@ -944,7 +951,18 @@ export async function runProviderQualification(runtime, scratchRoot, fixturePath
       imageInput: Boolean(imagePath),
       distinctSessionIds: true,
       overlapMs: Math.round(overlapMs),
+      promptAcceptedSamplesMs: [leftTurn.acceptedMs, rightTurn.acceptedMs].map(Math.round),
       promptAcceptedMs: summarizeMeasurements([leftTurn.acceptedMs, rightTurn.acceptedMs]),
+      agentStartSamplesMs: [leftTurn.agentStartMs, rightTurn.agentStartMs].map(Math.round),
+      agentStartMs: summarizeMeasurements([leftTurn.agentStartMs, rightTurn.agentStartMs]),
+      providerFirstEventSamplesMs: [
+        leftTurn.providerFirstEventMs,
+        rightTurn.providerFirstEventMs,
+      ].map(Math.round),
+      providerFirstEventMs: summarizeMeasurements([
+        leftTurn.providerFirstEventMs,
+        rightTurn.providerFirstEventMs,
+      ]),
       stopReasons: [leftTurn.stopReason, rightTurn.stopReason],
       abortIsolation: {
         abortedStopReason,