feat(events): restore inc_file_counts opt-in, session list layout + button polish

- Add `inc_file_counts` flag to `load_ae_obj_id__event_session` — maps to
  backend alt view (v_event_session_w_file_count) when true; default stays
  lightweight. Callers never pass raw view names.
- Preserve-on-write fallback in `_refresh_session_id_background` keeps
  cached file_count/file_count_all if API response omits them.
- Session detail +page.ts uses `inc_file_counts: true` so SvelteKit prefetch
  no longer clobbers counts via bulkPut on hover.
- Remove explicit `view: 'alt'` from launcher +page.ts (now invalid param).
- Session list link: flex-1 + min-w-0 for full-row width; name flex-1 pushes
  badge group right; code + file_count stacked in flex-col items-end.
- Hover styling: button-like appearance with slow fade-out (duration-500) /
  fast snap-in (hover:duration-150).
- Session +page.svelte: use url_session_id (string) for link_to_id props and
  auth__kv.session[] index — fixes TS type error from number|undefined.
- IDAA layout: dormant tech notice banner (guarded by 1==3, remove when ready).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/stores/ae_events_stores__pres_mgmt_defaults.ts

@@ -43,6 +43,7 @@ export interface PresMgmtLocState {
     show_content__session_search_room_name: boolean;
     show_content__session_view: string | null;
     show_content__session_qr: boolean;
+    hide__session_code: boolean;
     hide__session_msg: boolean;
     hide__session_poc: boolean;
     hide__session_poc_biography: boolean;
@@ -159,6 +160,7 @@ export const pres_mgmt_loc_defaults: PresMgmtLocState = {
     show_content__session_search_room_name: false,
     show_content__session_view: null,
     show_content__session_qr: false,
+    hide__session_code: true, // Default hidden; toggle in ae_comp__events_menu_opts to show
     hide__session_msg: true,
     hide__session_poc: true,
     hide__session_poc_biography: true,