Record R-AA landing, and two corrections it made to Soul's triage

Score 66% to 77.62%, every named survivor group killed, no production code
touched. The score is the least interesting part.

Two of the mutants Soul called live are equivalent: within one hop direction
the anchor and role already determine the target, so the pair cannot diverge.
They are recorded as equivalent so nobody pays for them a third time. And a
sixth mutant nobody had named survived in the same method on R-B's primary
ordering key, which means the rule R-B exists to protect had its first
component unguarded and the triage missed it.

The digest needed a golden value rather than a comparison. A same-versus-
different test cannot catch a mutant that swaps which case gets which flag,
because the two digests still differ, just mislabelled. The golden was
reconstructed from the method's documented contract rather than its own
helpers, which is what makes it evidence.

Three suspected real defects were flagged rather than quietly fixed, and get
behaviour tests first. The reachable one is an out-of-bounds read from an
attacker-supplied cursor.

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

docs/cultnet-selection-cut.md

@@ -2495,3 +2495,63 @@ Cut 2 spends it.
 - **Q-P. Ordering on a feed, later.** Out of this cut by the rules above.
   If "the latest N, live" is wanted, it is a third cut with an eviction
   rule, not a field added here.
+
+**R-AA landed, 2026-09-22** (Sonnet), `b7d77b7..99e366a` on
+`cultnet/selection-cut1`. One new test file, 27 tests, 707 lines. **No
+production code touched.** Score **66% → 77.62%**: killed 345→371, survived
+85→57, no-coverage 75→50, over the same 428-mutant set both passes. Suite
+green on Yggdrasil, 271 passed / 2 skipped.
+
+Every one of the nine named survivor groups is killed, with two corrections to
+the triage that matter more than the score.
+
+- **`EdgesFor`: three of five killed, and two are genuinely equivalent.**
+  Within one hop direction, `(From, Role)` already determines a unique
+  declared edge value, so no legal selection can make two edges share anchor,
+  From and Role while `To` differs. Hands could not construct one, and
+  Stryker agreed across two independent runs. **Soul's triage misclassified
+  `To.SchemaId` and `To.Key` as live.** They are recorded here as equivalent
+  so nobody pays for them a third time.
+- **A sixth mutant in the same method that nobody had named**:
+  `OrderBy(pageRowIndex)`, which is R-B's *primary* key, ahead of
+  `(from, role, to)`. It survived the first pass and is now killed by a test
+  that forces page order and `(from, role, to)` order to disagree. The rule
+  R-B exists to protect had its first component unguarded, and the triage had
+  not caught that either.
+- **The digest needed a golden value, not a comparison.** Beyond the named
+  branch mutants, about nineteen finer-grained ones survived — deleting
+  individual `AppendString` calls. A same-versus-different digest test
+  structurally cannot catch these: a mutant that swaps which case gets which
+  flag still produces two *different* digests, merely mislabelled. Hands
+  reconstructed a golden HMAC independently from the method's doc comments
+  rather than from its private helpers, which is the right way to build one,
+  and it killed all but three residual coincidences.
+
+**Line drift: every rule had moved 30–90 lines** from Soul's `52082ec`
+numbers, none to a different method. Locate by name, not by number, and do not
+trust the numbers in this section either.
+
+**Four things found along the way, flagged rather than silently fixed.** Two
+are test gaps; two look like real defects:
+
+- `ReadLengthPrefixedFields`, `length <= 0`: a legitimately zero-length field
+  would be wrongly refused.
+- `ReferenceMembers`'s `!member.IsReference` guard: a data member could be
+  treated as citeable.
+- `FindCursorPosition`'s loop bound: an out-of-bounds read when paging past
+  the last row with a cursor exactly at the end.
+- `ComputeDigest`'s `else`-branch appends survive only because the golden
+  test has both `Cites` and `Cited` non-null; a second golden with both absent
+  closes them.
+
+**Self's rulings, 2026-09-22:**
+
+- **R-AC. The two `EdgesFor` `To` mutants are equivalent.** Recorded, not to
+  be chased. A survivor correctly identified beats a test written to move a
+  number.
+- **R-AD. The three suspected defects above get behaviour tests first**, since
+  a test that fails today is the only thing that proves they are defects
+  rather than readings. The out-of-bounds read in `FindCursorPosition` is the
+  one to check first: it is reachable from an attacker-supplied cursor.
+- **R-AE. A second golden digest with both hops absent**, closing the three
+  residual mutants rather than leaving them as folklore.