upstream-sync 2026-07-13: merge conflicts need manual resolution

[Theralley]

Merging upstream/main (1be42992e64b08ff0dce3d7a914eaabf04284ffb, 68 new commits)
into main produced conflicts.

Resolve manually per docs/ant/upstream-sync.md §§1–2 (sentinel
rules), then push the sync branch and open the PR yourself.