fix(core-shared): satisfy strict typecheck in purge job + audit hook

The hoisted applyAction closure loses the collection narrowing (TS18048)
and apps with generated CollectionSlug unions reject comparing slugs to
'audit-logs' (TS2367). Re-bind the narrowed collection and widen the
slug comparison to string.

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

packages/core-shared/src/payload/retention-purge/retention-purge.job.ts

@@ -108,6 +108,9 @@ export function buildPurgeHandler(
     );
   }
 
+  // Re-bind after the guard: narrowing does not flow into hoisted closures.
+  const targetCollection = collection;
+
   const taskSlug = `retention-purge--${collectionSlug}`;
 
   async function applyAction(
@@ -120,7 +123,7 @@ export function buildPurgeHandler(
 
     if (action === "pseudonymize") {
       const piiFields: Record<string, null> = {};
-      for (const field of collection.fields) {
+      for (const field of targetCollection.fields) {
         const f = field as { name?: string; custom?: { pii?: unknown } };
         if (f.name && f.custom?.pii) {
           piiFields[f.name] = null;