POST /api/runs/stream and /api/runs/wait accept thread_id in the request
body but performed no owner authorization, letting any authenticated user
start runs on -- and read /wait checkpoint channel_values from -- another
user's thread (cross-user IDOR, #3472).
The @require_permission(owner_check=True) decorator resolves ownership from
the thread_id *path* param, so it cannot cover these body-param endpoints.
Enforce ownership inside start_run() before create_or_reject via
ThreadMetaStore.check_access: missing rows (auto-created temp threads) and
NULL-owner rows stay accessible, while a thread owned by another user
returns 404 (matching thread_runs.py). The internal system role (IM
channels acting for platform users) is exempt.
Closes#3472
ba9cc5e972