Append "Snapshot evidence (2026-05-13)" section to
`cancel_cascade_too_slow_under_main_thread_forkserver_issue.md`
documenting `fail_after_w_trace` diag capture results for
`test_nested_multierrors` under the MTF backend — reproduction cmd,
ptree analysis, observed hang signature, and updated triage plan.
(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
(cherry picked from commit 5372fd178a)
Gud Boi
db1baccf69