agent: Remove `thread-auto-capture` feature (#36474)

We never ended up using this in practice (the feature flag is not
enabled for anyone, not even staff)

Release Notes:

- N/A
e6d5a6a4fdBennet Bo Fenner committed on 8/19/2025, 10:59:34 AM· committed by GitHubparent790a2a0
4 files changedLine totals unavailable