LANDER.md section 7: record owner ruling anf3x2 on proven-equal plumbing merges (vault #3878 item 1)

roles/LANDER.md

@@ -1389,10 +1389,27 @@ routing consequence of both, and it is invisible until a worker hits it.
 | Why the lander can always write it | The banner edit is exempt from ownership whenever the heading is already on `origin/main`, which is exactly the closing case. |
 | When no worktree can be checked out | Build the commit with plumbing: `read-tree` into a temp index, `update-index`, `commit-tree`, push the resulting sha. It touches no working tree at all, so it cannot cause the collision the gate exists to prevent. |
 | The condition that keeps plumbing honest | State that you did so, and run by hand the checks pre-commit would have run. |
-| The scope limit on that escape | **It is sanctioned only while the content is YOURS.** On another seat's branch you cannot run their gates for them, and the same commands there become routing around a control. |
+| The scope limit on that escape | **It is sanctioned only while the content is YOURS.** On another seat's branch you cannot run their gates for them, and the same commands there become routing around a control. **WIDENED 2026-10-20, by owner rulings:** see *Owner ruling anf3x2*, below. |
 | Then hand it over STATED, not executed | Name the conflicting file, name the resolution, and say a seat with a working tree is needed. |
 | **NARROWED 2026-09-21.** That row is the last resort, not the first move | A CONTENT conflict is yours: cut a worktree and resolve it. Section *4c-quinquies*. Hand over only where you genuinely cannot reach the branch. |
 | Measured 2026-08-22 | A lander blocked by the worktree gate on two peer branches left a two-minute keep-both-sides resolution written out for whoever could reach the branch. That is a routing act, not a refusal. |
+| The exception to the scope limit above, by *Owner ruling anf3x2* | A plumbing merge commit on another seat's branch. The block below holds its scope and its proof. Any other plumbing on another seat's branch is still handed over stated. |
+
+**Owner ruling anf3x2.** Owner ruling 2026-10-10 (anf3x2), confirmed and its proof set by owner
+ruling 2026-10-20. The record is wiki event `20261010T010851106Z-anf3x2`, key
+`coord/merge/plumbing-after-worktree-gate`, on vault `main`.
+
+After the worktree gate refuses `git merge`, a merge commit built with `merge-tree` then
+`commit-tree` is allowed on another seat's branch only when proven equal to a normal merge.
+
+The proof has three parts, and each is required:
+
+1. The same tree as an independent merge.
+2. A remerge-diff that is empty, or whose conflict resolution had its own code review.
+3. Checks recorded on the PR.
+
+This playbook records the ruling for the Lander, and recording it here grants no other seat anything.
+A Builder whose gate refuses still stops and reports.
 
 ### 7c. The BACKLOG tail is a serialization point, and so is the ADR index