Codex review found three gaps between the documented contract and what
the gate enforced, each proven by a failing probe before this fix:
- a generated region must sit directly under its own '## {Lifecycle}'
heading (the last H2 above the begin marker), so a drifted heading
can no longer leave the tables filed under the wrong section;
- the lifecycle set is closed like the class set: an unknown directory
under docs/rfc/ is a structure error, not an invisible subtree;
- an index-shaped table row linking into a lifecycle folder OUTSIDE the
generated regions is an error (prose links to RFCs stay legal), so
'listed exactly once' cannot be violated by a hand-added row.
Tianyi Cui
226a8b5e4c