Three related fixes for the hide/show toggle in Pres Mgmt:
1. ae_events__event_session.ts: remove redundant search_query.and hide
filter and instead pass `hidden` to api.search_ae_obj as a URL param.
The backend StatusFilterParams defaults to hidden='not_hidden', so
without this the API always filtered to hide=0 regardless of intent.
2. pres_mgmt/+page.svelte (SCENARIO 2): capture qry_hidden as a
$derived.by dependency so the liveQuery instance is recreated on
toggle — prevents hidden sessions briefly appearing before the
debounce fires (blink fix).
3. pres_mgmt/+page.svelte (API call): use params.qry_hidden snapshot
instead of the live store to prevent race if user toggles during a
pending search.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>