fix: auto-recover primary model after rate-limit cooldown expires (#17478) (#18045)

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

Prepared head SHA: f7a7865727
Co-authored-by: PlayerGhost <28265945+PlayerGhost@users.noreply.github.com>
Co-authored-by: sebslight <19554889+sebslight@users.noreply.github.com>
Reviewed-by: @sebslight

src/agents/auth-profiles/usage.ts

@@ -25,6 +25,32 @@ export function isProfileInCooldown(store: AuthProfileStore, profileId: string):
   return unusableUntil ? Date.now() < unusableUntil : false;
 }
 
+/**
+ * Return the soonest `unusableUntil` timestamp (ms epoch) among the given
+ * profiles, or `null` when no profile has a recorded cooldown. Note: the
+ * returned timestamp may be in the past if the cooldown has already expired.
+ */
+export function getSoonestCooldownExpiry(
+  store: AuthProfileStore,
+  profileIds: string[],
+): number | null {
+  let soonest: number | null = null;
+  for (const id of profileIds) {
+    const stats = store.usageStats?.[id];
+    if (!stats) {
+      continue;
+    }
+    const until = resolveProfileUnusableUntil(stats);
+    if (typeof until !== "number" || !Number.isFinite(until) || until <= 0) {
+      continue;
+    }
+    if (soonest === null || until < soonest) {
+      soonest = until;
+    }
+  }
+  return soonest;
+}
+
 /**
  * Mark a profile as successfully used. Resets error count and updates lastUsed.
  * Uses store lock to avoid overwriting concurrent usage updates.