fix: add non-null assertions for Uint32Array index access in sortValues

noUncheckedIndexedAccess causes Uint32Array element access to return
number | undefined. Since loop bounds guarantee valid indices, use !
to assert non-null and satisfy the type checker.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

src/core/series.ts

@@ -754,23 +754,23 @@ export class Series<T extends Scalar = Scalar> {
     let pos = 0;
     if (naPosition === "first") {
       for (let i = 0; i < nanCount; i++) {
-        const idx = nanBuf[i];
+        const idx = nanBuf[i]!;
         perm[pos] = idx;
         outData[pos++] = vals[idx] as T;
       }
       for (let i = 0; i < finCount; i++) {
-        const idx = finSlice[i];
+        const idx = finSlice[i]!;
         perm[pos] = idx;
         outData[pos++] = vals[idx] as T;
       }
     } else {
       for (let i = 0; i < finCount; i++) {
-        const idx = finSlice[i];
+        const idx = finSlice[i]!;
         perm[pos] = idx;
         outData[pos++] = vals[idx] as T;
       }
       for (let i = 0; i < nanCount; i++) {
-        const idx = nanBuf[i];
+        const idx = nanBuf[i]!;
         perm[pos] = idx;
         outData[pos++] = vals[idx] as T;
       }