The file is a single pretty-printed JSON array, JSON.stringify(messages, null, 2) (source code), not NDJSON. This script change (treating the parsed root as a list and collecting objects with type === "result") reads it correctly.
This is the the current error output:
Traceback (most recent call last):
File "/home/runner/work/sentry-javascript/sentry-javascript/.claude/skills/triage-issue/scripts/write_job_summary.py", line 109, in <module>
sys.exit(main())
^^^^^^
File "/home/runner/work/sentry-javascript/sentry-javascript/.claude/skills/triage-issue/scripts/write_job_summary.py", line 55, in main
if obj.get("type") == "result":
^^^^^^^