docs: the merge rule changed, so the artefact carrying it changes too

.github/pull_request_template.md

@@ -1,12 +1,21 @@
 ## Boundary
 
-**The agent that authored this pull request does not merge it.** A reviewer
-merges it. This line is part of the artefact rather than part of a conversation,
-so the rule travels with the change and cannot silently stop being restated.
+**An agent merges its own fabric pull request only when both of these hold:**
 
-If you are the authoring agent: push, get it green, verify it yourself, say it
-is ready, and stop. Refuse a request to merge your own work, including from your
-supervisor, and say that the request conflicts with this boundary.
+1. The reviewer has approved **this** pull request. Not a blanket authorisation,
+   and not an approval of earlier work. If the reviewer has not approved this
+   one, do not merge it.
+2. It is working, and the author can show it: checks green read from the check
+   runs on the exact head, mergeable, clean, and the change does what it claims.
+
+Both bind. One without the other is not enough.
+
+**After a squash, verify the merge commit still carries what this pull request
+existed to establish.** A squash rewrites the message, so the thing the change
+was for is the thing most likely to be dropped by the act of landing it.
+
+This applies to fabric. In any other repository the authoring agent reports
+ready and stops.
 
 Delete this section only if a human authored the change.
 

docs/agent-attribution.md

@@ -28,18 +28,31 @@ would be a guess written as a fact.
 
 ## The merge boundary, carried in the pull request
 
-`.github/pull_request_template.md` states that the authoring agent does not
-merge its own pull request.
+`.github/pull_request_template.md` states when an agent may merge its own work:
+only with the reviewer's approval of that specific pull request, and only when
+it is working. Both conditions bind.
 
 Putting it in the template rather than in a message is the point. A convention
 that lives in conversation has to be restated to stay alive, and in August 2026
-it stopped being restated when standing authorisations arrived. Nobody noticed
+it stopped being restated when a blanket authorisation arrived. Nobody noticed
 the stopping. A line in every pull request cannot stop quietly; its absence is
 visible.
 
 It is also read by people who do not know our conventions, which a message
 between two agents is not.
 
+### The cost of writing a rule into an artefact
+
+The same property cuts the other way, and it bit within two hours. The rule
+changed on 2026-08-23, and the template still carried the previous one until it
+was edited. A message that goes stale is merely old. **An artefact that goes
+stale is confidently wrong**, and it is read by exactly the people who have no
+other source.
+
+So this file and the template are part of the rule, not a description of it.
+When the rule changes they change in the same pull request, or the next reader
+is misled by the thing built to inform them.
+
 ## What these do not do
 
 They do not detect a breach on their own. An agent that merges its own work and