Extend GitHub release read retries and add jitter (#57796)

Increase GitHub release reads for contract runners from three to five
attempts, with base retry delays of 2, 5, 15, and 45 seconds. Add random
jitter of up to half the base delay before each retry.

GitOrigin-RevId: 9d66ab21a7f7646a9f737e65c08284e82f39991b

.github/scripts/contract_releases.py

@@ -1,6 +1,7 @@
 """Discover and download published Codex packages for contract runners."""
 
 import json
+import random
 import re
 import subprocess
 import sys
@@ -16,7 +17,7 @@ PACKAGE = "codex-package-x86_64-unknown-linux-musl.tar.gz"
 
 def github_read(args: list[str]) -> str:
     """Retry release reads unless the error is known permanent; never retry verification."""
-    for attempt, delay in enumerate((2, 5, 0), start=1):
+    for attempt, delay in enumerate((2, 5, 15, 45, 0), start=1):
         try:
             return subprocess.check_output(
                 args, text=True, stderr=subprocess.PIPE, timeout=120
@@ -58,6 +59,7 @@ def github_read(args: list[str]) -> str:
             )
             if not will_retry:
                 raise
+            delay += random.randint(0, delay // 2)
             print(f"Retrying GitHub release read in {delay}s.", file=sys.stderr)
             time.sleep(delay)