Operating rules: the nine things a fresh session must not have to rediscover

Project folder convention, how a task is judged finished, content-bound approvals, untrusted
text as data, secret handling, ocr review and serialised merge, one project per machine,
cost limits, and the four commands that already work. Referenced from AGENTS.md.

AGENTS.md

@@ -85,6 +85,14 @@ Only the first item of `CHECKLIST.md`. One task, really run, with no interface.
 
 Do not start the Go program until that passes.
 
+## Operating rules
+
+`docs/OPERATING-RULES.md` is not optional reading. It has nine rules: the project folder
+convention, how a task is judged finished (a command agreed beforehand), approvals being
+content-bound, untrusted text being data, how secrets are handled, `ocr` review and
+serialised merges, one project per machine, cost limits, and the four commands that already
+work (`office`, `office --host`, `project-reset`, `board`).
+
 ## Things that are ours, because Paperclip does not do them
 
 - One project = one folder on one machine, and remembering which machine it is on.