R-267 addendum: read the cast, do not copy it

I told the scenario session that this guard turns a silent re-cast into a build
failure, and it accepted the coupling on that basis. The cast was hardcoded, so
a re-cast would have left it measuring the old six and reporting success.

Reads the <!-- cast: --> marker check-rollable established, drops the two the
scaling note drops by name rather than by position, and refuses to run if the
marker is gone. Verified by re-casting CLEAN GROUND in a throwaway worktree and
watching the guard name the change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/REVIEW_LOG.md

@@ -5898,3 +5898,21 @@ not wrong enough to mislead anybody and it was wrong enough to print.
 at twelve, which is exactly the hardcoded-list failure its own comment warns about two
 lines above, committed by the file that exists to prevent it. Extended to sixteen, which
 defers the same defect rather than curing it.
+
+**Addendum — the coupling did not actually bite.** I told the scenario's session that this
+guard converts a silent re-cast into a build failure. It believed me and accepted the
+coupling on that basis. It was not true: the cast was written out by hand here, so a
+re-cast would have left this measuring the old six and reporting success — the project's
+own signature defect, committed inside the guard written to prevent a weaker version of
+it, three hours after writing "a claim nothing checks" about something else.
+
+It now reads the `<!-- cast: ... -->` marker check-rollable already established, derives
+the cut by dropping the two the scaling note drops — by name, since "the first four" would
+survive a reordering and quietly measure different people — and refuses to run at all if
+the marker is missing. Proved by re-casting CLEAN GROUND in a throwaway worktree and
+watching it fail: *"cut: the scenario now casts different people — no longer braithwaite,
+now agyeman ... re-record with --update, do not revert the cast."*
+
+**Which is the third time in this sequence that a thing was true only because nobody had
+tested it.** The generator comment, the costed restraint, and now the coupling — each
+stated confidently, each wrong, each found by somebody trying it rather than reading it.