style(frontend): tidy drawer review nits

- RawSegmentsPanel: summary now reads 'Show N raw segments' for
  non-empty (with singular pluralization). The previous identical
  ternary branches read as a bug.
- PartiesGrid: replace the verbose intersection cast on AddressBlock
  with a direct ClaimDetailAddress cast (the union's other arm is
  Record<string, never>, ruled out by isEmptyAddress above).

src/components/ClaimDrawer/PartiesGrid.tsx

@@ -1,4 +1,4 @@
-import type { ClaimDetail } from "@/types";
+import type { ClaimDetail, ClaimDetailAddress } from "@/types";
 
 type PartiesGridProps = {
   parties: ClaimDetail["parties"];
@@ -20,15 +20,9 @@ function isEmptyAddress(addr: AddressLike | null | undefined): boolean {
 
 function AddressBlock({ address }: { address: AddressLike }) {
   if (isEmptyAddress(address)) return null;
-  // After the empty check the cast is safe; the alternative `ClaimDetailAddress`
-  // shape has all the fields we read.
-  const a = address as ClaimDetail["parties"]["billingProvider"]["address"] & {
-    line1: string;
-    line2: string | null;
-    city: string;
-    state: string;
-    zip: string;
-  };
+  // After the empty check the cast is safe — the remaining union arm is
+  // `ClaimDetailAddress` which has all the fields we read.
+  const a = address as ClaimDetailAddress;
   return (
     <div
       className="text-xs leading-relaxed text-[color:var(--m-ink-secondary)]"

src/components/ClaimDrawer/RawSegmentsPanel.tsx

@@ -44,8 +44,8 @@ export function RawSegmentsPanel({ rawSegments }: RawSegmentsPanelProps) {
           data-testid="raw-segments-summary"
         >
           {rawSegments.length === 0
-            ? "Show raw segments"
-            : "Show raw segments"}
+            ? `Show raw segments`
+            : `Show ${rawSegments.length} raw segment${rawSegments.length === 1 ? "" : "s"}`}
         </summary>
 
         {rawSegments.length === 0 ? (