[TASK] Finish the ARIA grid wiring on the shared folder list view

Parent

Follow-up from #32591 / PR #37436 (Content Drive keybindings). Raised in review.

Problem

dot-folder-list-view now sets [attr.aria-selected] on every row, but the container is still
PrimeNG's default role="table". aria-selected is only fully meaningful on a row inside
role="grid" (or a listbox/tree), so some assistive technology ignores it, and the listing's
selection state is not reliably announced.

aria-multiselectable was tried and removed in the same PR: role="table" does not support it, so
it was wiring that only looked connected.

Why it was not done in #37436

Switching to role="grid" brings the grid keyboard contract with it. A screen reader enters focus
mode on a grid row, and Left/Right — which today read cell by cell in browse mode — would do nothing,
because cell-level navigation is not implemented. Half a grid is a worse listing to read than a
table, so the role was left alone and the gap recorded.

What "done" looks like

• role="grid" on the table, aria-multiselectable driven by selectionMode
• Left/Right arrow navigation between cells within the focused row, per the APG grid pattern
• aria-rowcount / aria-rowindex on a paginated listing, so position is announced against the
  full result set rather than the rendered page
• Verified against a real screen reader (NVDA and VoiceOver), not only unit assertions

Where

• core-web/libs/ui/src/lib/components/dot-folder-list-view/dot-folder-list-view.component.html
  (row block comment records the current decision)
• core-web/libs/ui/src/lib/components/dot-folder-list-view/dot-folder-list-view.component.ts
  ($ptConfig)

Shared by Content Drive, the Asset Picker and the Action Center preview, so a change here is
cross-portlet.

Start in core-web/libs/ui/src/lib/components/dot-folder-list-view/dot-folder-list-view.component.html, reading the row block comment and current table wiring, then inspect dot-folder-list-view.component.ts around $ptConfig. Trace the shared Content Drive, Asset Picker and Action Center preview uses. Done means the grid role, selection state, cell navigation and paginated row positions work, verified with NVDA and VoiceOver.