repair: resolve the merge conflict left in DECISIONS.md

[matthewpmunger]

Base commit

• Base sha: 70bfbb332b5018e6a26cc29b99541bcdc631af6b
• Checks at that sha: green — npm run lint, npm run typecheck,
  npm test -- --run (103 files / 1324 tests), npm run build all pass.

What & why

A repair, claimed in REPAIRS.md before it was written, and labelled repair.

DECISIONS.md on main contains a literal unresolved merge conflict in its
intro paragraph — <<<<<<< HEAD, =======, >>>>>>> origin/main at lines
3–13. It was committed in aeeca8b ("Merge main (S8, PERSON fix) into S4") and
shipped through PR #88 with CI green, because no check reads markdown.

This is the fifth instance of the pattern R3 was written for, one layer out: two
sessions edited the same paragraph, the merge needed a human answer, and the
answer never came. Green CI is not a green main.

Changes

Three commits, deliberately separate:

1. cf829fb — the claim. Takes the open row in REPAIRS.md, pushed and
   opened as a PR before the fix existed, so a second session finds the claim
   instead of writing a second fix. That is the failure mode this ledger came
   from: F5 and R2 both repaired F4's caller sweep, git found no conflict, took
   both copies, and fix: one PERSON caller per test file, not two #87 had to delete the duplicates.
2. The repair itself, alone in its own commit so it can be reviewed or
   reverted without the bookkeeping. It keeps the un-counted wording (from S4,
   b9870b8) and deletes the stale side (from S8, 296106d), which still said
   "five previously-undefined product questions" and "a one-line edit". The file
   has six numbered decisions and decision 6 is not a one-line edit, so the
   surviving side is the one that is true. No decision's content is touched.
3. The ledger row moves to Landed.

Verification

• npm run lint passes (at base 70bfbb3)
• npm run typecheck passes
• npm test -- --run passes
• npm run build passes
• git grep -n '<<<<<<<\|=======\|>>>>>>>' finds no conflict markers left in
  the repo
• n/a No route change: markdown only, no product code.

Notes

• The repair label is the claim's visibility, not a bypass here: main is
  green, so base-branch-green passes on its own merits and nothing is waived.
• Worth knowing that no check reads markdown. This PR does not add one — the
  defect was a merge left unresolved, not a missing check, and R3's rule is that
  a process defect gets a process fix. If we later want conflict markers to be
  impossible to commit, that is its own small change and its own argument.