fix(ui): prioritize providedRowCount in useTable hook

Changed the row count calculation in the useTable hook to prioritize
the providedRowCount prop over data.length. This ensures accurate
row count values in server-side pagination scenarios where the total
number of rows differs from the current page's data length.

Signed-off-by: Johan Persson <johanopersson@gmail.com>

.changeset/spicy-teeth-study.md

@@ -0,0 +1,5 @@
+---
+'@backstage/ui': patch
+---
+
+Fixed `useTable` hook to prioritize `providedRowCount` over data length for accurate row count in server-side pagination scenarios.

packages/ui/src/components/Table/hooks/useTable.ts

@@ -50,8 +50,8 @@ export function useTable<T = any>(
   const isControlled =
     controlledOffset !== undefined || controlledPageSize !== undefined;
 
-  // Calculate row count from data or use provided value
-  const rowCount = data?.length ?? providedRowCount ?? 0;
+  // Use providedRowCount if passed, otherwise fallback to data length
+  const rowCount = providedRowCount ?? data?.length ?? 0;
 
   // Internal state for uncontrolled mode
   const [internalOffset, setInternalOffset] = useState(defaultOffset);