feat: inherit model-picker reorder/accordion persistence and shift-delete from otto-ui (#1833)

* feat(model-picker): drag-to-reorder providers and persist accordion state

Ports two model/provider picker QoL features from otto-ui:
- Persist collapsed state of picker sections (favorites, recent, each
  provider) via a new persisted zustand store so collapse survives
  remounts and reloads, shared across every picker surface.
- Desktop drag-to-reorder of provider sections (whole header as the
  mouse activator, 8px threshold so a plain click still toggles
  collapse), with the order persisted in useUIStore.providerOrder and
  applied across ModelControls, ModelMultiSelect and ModelSelector.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* feat(sessions): shift-click quick action hard-deletes thread without prompt

Ports the shift-quick-delete feature from otto-ui. The sidebar quick
action (normally archive) becomes a no-prompt hard delete while Shift is
held: the icon switches to a trash bin, the affordance turns destructive,
and the click bypasses the confirmation dialog via a new skipConfirm
source flag. A shared useShiftKeyHeld hook (single window listener set,
useSyncExternalStore) keeps only the small action button re-rendering on
Shift state changes, and resets on window blur so the affordance can't
get stuck after alt-tab.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

---------

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/components/session/sidebar/hooks/useSessionActions.ts

@@ -15,6 +15,8 @@ type DeleteSessionConfirmSetter = React.Dispatch<React.SetStateAction<{
 type DeleteSessionSource = {
   archivedBucket?: boolean;
   hardDelete?: boolean;
+  /** Bypass the confirmation dialog and delete/archive immediately. */
+  skipConfirm?: boolean;
 };
 
 type Args = {
@@ -253,7 +255,7 @@ export const useSessionActions = (args: Args) => {
         collectDescendants(session.id),
         shouldHardDelete,
       ).map((s) => s.id);
-      if (!args.showDeletionDialog) {
+      if (!args.showDeletionDialog || source?.skipConfirm === true) {
         void executeDeleteSession(session, source, { descendantIds: effectiveDescendantIds });
         return;
       }