The pointers back from what yesterday's records changed, which I missed twice

Three records were left describing a mechanism a new record had moved,
and a reader arrives at them by following a citation: 0066 still said a
routed name is written into every container after 0148 replaced that with
resolution; 0016 still read as though the lab were the test bed after
0149; and issues 109 and 135 said nothing about 0148 ending the copying
that 135's own fix made comparable. Each was a citation leading to the
wrong answer in a record that was not wrong about anything it decided.

This is the second time in one session. The playbook rule I added last
round did not stop it, so the convention is now written where the record
conventions live, with the shape to use and three worked examples — and
with the honest note that it is NOT machine-checked and cannot be from
`extends:` alone: 102 records extend another, 87 have no back-reference,
and that is correct, because extending usually means building on a
context. Making it mechanical means a record declaring the relationship
in frontmatter, which is a schema change and is not mine to decide.

Also: designs 18 and 20 claimed `updated:` dates from before I edited
them, and 117's `fixed-by` gained the commit beside the record.

02-DECISIONS/README.md

@@ -48,6 +48,31 @@ form above and dated no earlier than the record's own `date:` — an unmarked ed
 violation the reviewer looks for in the diff, and a marked one is legible in the record itself.
 The git history is the backstop, not the record of intent; the note is the record of intent.
 
+## A pointer back from what a record changes
+
+A new record naming an old one is not enough. **Where a record changes a mechanism an older record
+states — without reversing the decision, so no supersession — the older record gets a dated note
+saying where its mechanism now lives.** A reader arrives at the old record by following a citation,
+and finds text that is still the decision and no longer the method; nothing in it says a later record
+moved the method, and the new record is not in their hands.
+
+> **The mechanism changed — YYYY-MM-DD, by ADR NNNN.** What still stands, what moved,
+> and why.
+
+Three examples of the shape, all found by being missed: ADR 0066 still described a routed name being
+written into every container after 0148 replaced that with resolution; ADR 0047 still said a module's
+code runs in a container after 0150 made it a supervised process; and ADR 0016 still read as though the
+lab were the test bed after 0149 said the live mesh is. Each was a citation leading to the wrong
+answer, in a record that was not wrong about anything it decided.
+
+**This is not machine-checked, and it cannot be from `extends:` alone.** 102 records extend another and
+87 name a parent that does not mention them, which is correct: extending usually means building on a
+context, and a one-directional pointer is the right shape for that. What needs a note is the narrower
+case where the parent's own text has gone stale, and which case that is, is a judgement — so it is a
+rule for the author and the reviewer, and the diff is where it is caught. Making it mechanical would
+mean a record declaring the relationship in its frontmatter, which is a change to the record schema and
+has not been decided.
+
 The records run in the order the decisions were taken, oldest first.
 
 **Every decision is a record.** There is no ledger and no index file — if a decision is worth