fix(rectification): stop a stale candidate-set prefix from hiding the choice card

Scoring scoped the contrast packet to the previous round's candidate set while
minting probes for the new one, so every later read re-prefixed the stored hash
and the persisted focus schema could never match. Mint one prefix per set and
compare splits by probe identity.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVapmh2oGNyr6ECHKjPJY8

frontend/src/lib/rectification-agentic/v9/method-followup.ts

@@ -63,6 +63,7 @@ import { decideRectification, type HoldoutValidationStatus } from "../core/recti
 import {
   datedDomainsFromEvidence,
   isStructuredDiscriminator,
+  isSameCandidateSplit,
   mentionedVargaKeysFromLedgerEvidence,
   vargaLayerCovered,
   vargaLayerFromSemanticKey,
@@ -1818,7 +1819,14 @@ export function projectRectificationChoiceCard(
     : null;
   if (input.activeFocus?.intent !== followup.intent) return null;
   if (followup.semantic_key && schemaRow?.semantic_key !== followup.semantic_key) return null;
-  if (followup.candidate_split_hash && schemaRow?.candidate_split_hash !== followup.candidate_split_hash) return null;
+  if (
+    followup.candidate_split_hash
+    && !isSameCandidateSplit(
+      typeof schemaRow?.candidate_split_hash === "string" ? schemaRow.candidate_split_hash : null,
+      followup.candidate_split_hash,
+      followup.semantic_key,
+    )
+  ) return null;
   if (
     !followup.semantic_key
     && !followup.candidate_split_hash