chore: import upstream snapshot with attribution

apps/sim/lib/guardrails/pii-batching.ts

@@ -0,0 +1,41 @@
+/**
+ * Per-request bounds shared by both Presidio hops: the app→route HTTP call
+ * (`mask-client`) and the route→service call (`validate_pii`). Keeping a single
+ * source of truth ensures every request stays far under the 10MB Next body limit
+ * and small enough for one short spaCy NER pass per Presidio request.
+ */
+
+/** Max UTF-8 bytes of text per Presidio request. ~40× under the 10MB Next limit. */
+export const PII_REQUEST_MAX_BYTES = 256 * 1024
+/** Max strings per request; caps per-item overhead and stays well under the contract's 100k-entry cap. */
+export const PII_REQUEST_MAX_COUNT = 2_000
+
+/**
+ * Group `texts` into chunks of original indices, flushing a chunk when adding the
+ * next string would exceed {@link PII_REQUEST_MAX_BYTES} or {@link PII_REQUEST_MAX_COUNT}.
+ * A single string larger than the byte budget still gets its own chunk — strings
+ * are never dropped, since an unredacted leaf would persist PII. Order is preserved
+ * across and within chunks.
+ */
+export function chunkIndicesByBudget(texts: string[]): number[][] {
+  const chunks: number[][] = []
+  let current: number[] = []
+  let bytes = 0
+
+  for (let i = 0; i < texts.length; i++) {
+    const size = Buffer.byteLength(texts[i], 'utf8')
+    if (
+      current.length > 0 &&
+      (current.length >= PII_REQUEST_MAX_COUNT || bytes + size > PII_REQUEST_MAX_BYTES)
+    ) {
+      chunks.push(current)
+      current = []
+      bytes = 0
+    }
+    current.push(i)
+    bytes += size
+  }
+  if (current.length > 0) chunks.push(current)
+
+  return chunks
+}