fix(opencode): retry xAI capacity stream errors (#43640)

Co-authored-by: rekram1-node <rekram1-node@users.noreply.github.com>

packages/opencode/test/session/retry.test.ts

@@ -215,6 +215,9 @@ describe("session.retry.retryable", () => {
     "response timed out",
     "Please retry your request",
     "try your request again",
+    "Please try again in a few minutes",
+    "The model is currently at capacity due to high demand",
+    "The service is temporarily at capacity",
     "upstream returned status 524",
   ])("retries matching API error text: %s", (message) => {
     expect(SessionRetry.retryable(wrap(message), retryProvider)).toEqual({ message })