ui: sort the file manager tree by FID or symbolic name

- pysimFsSortChildren() groups DFs above EFs, then sorts each group by
  FID (default) or case-insensitive symbolic name; missing names fall
  back to the FID as the sort key; deterministic tie-break; the input
  array is not mutated
- render uses the sorted copy, so lazily loaded directories and custom
  file injections are sorted too
- FID / Name pills above the tree (pysimFsSetSort) persist the choice in
  localStorage (otaman_fs_sort) and re-render without refetching
- tests for the comparator (DF priority, both keys, fallbacks, custom
  entries, no mutation) and the pill wiring; help/README updated;
  SW cache v108 -> v109.

frontend/tests/html.test.js

@@ -48,3 +48,9 @@ test('header state indicator and profiler custom-files tab', () => {
     assert.ok(html.includes('data-list-tab="custom"'));
     assert.ok(!html.includes('data-pysim-sub="custom"'));
 });
+
+test('file manager has FID / Name sort pills', () => {
+    assert.match(html, /data-fs-sort="fid" onclick="pysimFsSetSort\('fid'\)"/);
+    assert.match(html, /data-fs-sort="name" onclick="pysimFsSetSort\('name'\)"/);
+    assert.ok(html.includes('pysim-fs-sort-pill'));
+});