feat(sp29): inbox rejected-row 999 ack chips + per-row Resubmit

- backend: _ack_summary_for_claims helper attaches claim_acks payload
  to inbox rejected-lane rows (3 tests)
- frontend: InboxRow renders newest 3 AK2 chips + '+N more' overflow
  under the rejection reason, with '999 not linked' marker when an
  ack couldn't be linked to a claim
- frontend: per-row Resubmit button downloads a single corrected 837
  via api.serializeClaim837 (no bulk modal, no zip — one click, one
  .x12 file)
- frontend: 2 new tests for the chip rendering and the per-row
  download flow

src/components/inbox/InboxRow.tsx

@@ -10,6 +10,8 @@ const ACCENT_VAR: Record<Accent, string> = {
   muted: "var(--tt-muted)",
 };
 
+const REJECT_CODES = new Set(["R", "E", "X"]);
+
 function fmtMoney(n: number | null | undefined): string {
   if (n == null) return "—";
   return n.toLocaleString("en-US", { style: "currency", currency: "USD" });
@@ -55,12 +57,54 @@ function Sparkline({ breakdown }: { breakdown: ScoreBreakdown | null }) {
   );
 }
 
-type Props =
-  | { row: InboxClaimRow; accent: Accent; onClick: () => void }
-  | { row: InboxCandidateRow; accent: Accent; onClick: () => void };
+// ---------------------------------------------------------------------------
+// SP29: per-AK2 chip (compact evidence row for the rejected-lane drill)
+// ---------------------------------------------------------------------------
+function AckCodeChip({
+  setControlNumber,
+  code,
+}: {
+  setControlNumber: string;
+  code: string;
+}) {
+  const isReject = REJECT_CODES.has(code);
+  return (
+    <span
+      className="inline-flex items-center gap-1 rounded-sm border px-1.5 py-0.5 mono tabular-nums"
+      style={{
+        fontSize: 9.5,
+        letterSpacing: "0.04em",
+        color: isReject ? "var(--tt-oxblood)" : "var(--tt-muted)",
+        backgroundColor: isReject
+          ? "rgba(229, 72, 77, 0.08)"
+          : "rgba(220, 220, 230, 0.06)",
+        borderColor: isReject
+          ? "rgba(229, 72, 77, 0.28)"
+          : "rgba(220, 220, 230, 0.20)",
+        fontWeight: 600,
+      }}
+      title={`ST02 ${setControlNumber} · AK5 ${code}${isReject ? " (rejected)" : " (accepted)"}`}
+    >
+      <span style={{ opacity: 0.7 }}>{setControlNumber}</span>
+      <span>·</span>
+      <span style={{ fontWeight: 700 }}>{code || "—"}</span>
+    </span>
+  );
+}
 
-export function InboxRow({ row, accent, onClick }: Props) {
+type Props = {
+  row: InboxClaimRow | InboxCandidateRow;
+  accent: Accent;
+  onClick: () => void;
+  /** SP29: per-row Resubmit gesture. Only meaningful for rejected
+   *  claim rows; the component no-ops on remit rows or other states. */
+  onResubmitOne?: (claimId: string) => void;
+};
+
+export function InboxRow({ row, accent, onClick, onResubmitOne }: Props) {
   const isCandidate = row.kind === "remit";
+  const isRejected =
+    !isCandidate && (row as InboxClaimRow).state === "rejected";
   const id = isCandidate ? (row as InboxCandidateRow).payer_claim_control_number : row.id;
   const payer = (isCandidate ? (row as InboxCandidateRow).payer_id : (row as InboxClaimRow).payer_id) ?? "";
   const charge = fmtMoney(row.charge_amount);
@@ -68,6 +112,7 @@ export function InboxRow({ row, accent, onClick }: Props) {
   const rejectedAt = !isCandidate ? (row as InboxClaimRow).rejected_at : null;
   const topScore = isCandidate && row.candidates.length > 0 ? row.candidates[0].score : null;
   const filled = isCandidate && row.candidates.length > 0 ? row.candidates[0].breakdown : null;
+  const claimAcks = !isCandidate ? (row as InboxClaimRow).claim_acks : null;
 
   return (
     <tr
@@ -93,7 +138,47 @@ export function InboxRow({ row, accent, onClick }: Props) {
         className="py-2.5 mono"
         style={{ color: reason ? "var(--tt-oxblood)" : "var(--tt-amber)", fontSize: 11 }}
       >
-        {reason ?? (topScore != null ? `score ${topScore}` : "")}
+        <div className="flex flex-col gap-1">
+          <span>{reason ?? (topScore != null ? `score ${topScore}` : "")}</span>
+          {/* SP29: rejected-lane AK2 chip evidence (newest 3 + overflow). */}
+          {isRejected && claimAcks && claimAcks.items.length > 0 && (
+            <span className="inline-flex items-center gap-1 flex-wrap">
+              {claimAcks.items.slice(0, 3).map((it) => (
+                <AckCodeChip
+                  key={`${it.ack_id}-${it.ak2_index}`}
+                  setControlNumber={it.set_control_number}
+                  code={it.set_accept_reject_code}
+                />
+              ))}
+              {claimAcks.total > 3 && (
+                <span
+                  className="inline-flex items-center rounded-sm border px-1.5 py-0.5 mono tabular-nums"
+                  style={{
+                    fontSize: 9.5,
+                    letterSpacing: "0.04em",
+                    color: "var(--tt-muted)",
+                    borderColor: "rgba(220, 220, 230, 0.20)",
+                    backgroundColor: "rgba(220, 220, 230, 0.04)",
+                    fontWeight: 600,
+                  }}
+                  title={`${claimAcks.total - 3} more AK2 set-response(s) on the ClaimDrawer`}
+                >
+                  +{claimAcks.total - 3} more
+                </span>
+              )}
+            </span>
+          )}
+          {/* SP29: rejected claim but no linked 999 acks (orphan). */}
+          {isRejected && (!claimAcks || claimAcks.items.length === 0) && (
+            <span
+              className="mono italic"
+              style={{ fontSize: 10, color: "var(--tt-muted)", opacity: 0.75 }}
+              title="No 999 AK2 set-responses are linked to this claim. The set_control_number on the 999 ack had no matching ST02 batch. Use the Inbox ack-orphans lane to manually match."
+            >
+              999 not linked
+            </span>
+          )}
+        </div>
       </td>
       <td
         className="py-2.5 mono tabular-nums"
@@ -116,6 +201,35 @@ export function InboxRow({ row, accent, onClick }: Props) {
       <td className="py-2.5 pr-3">
         <Sparkline breakdown={filled} />
       </td>
+      {/* SP29: per-row Resubmit button (rejected-lane only). */}
+      {isRejected && onResubmitOne ? (
+        <td
+          className="py-2.5 pr-3 text-right"
+          onClick={(e) => e.stopPropagation()}
+        >
+          <button
+            type="button"
+            className="mono uppercase tracking-[0.12em] px-2 py-1 rounded-sm transition-colors hover:bg-[color:var(--tt-amber)]/10 focus-visible:outline-none focus-visible:bg-[color:var(--tt-amber)]/10"
+            style={{
+              color: "var(--tt-amber)",
+              border: "1px solid rgba(229, 154, 50, 0.40)",
+              backgroundColor: "transparent",
+              fontSize: 10,
+              fontWeight: 700,
+            }}
+            data-testid={`resubmit-${id}`}
+            onClick={(e) => {
+              e.stopPropagation();
+              onResubmitOne(id);
+            }}
+            title="Download the corrected 837 for this single claim"
+          >
+            Resubmit
+          </button>
+        </td>
+      ) : (
+        <td className="py-2.5 pr-3" aria-hidden />
+      )}
     </tr>
   );
 }