fix(launcher): hidden sessions collapse space, sort by datetime, rename internal-file flag

- menu_session_list: move class:hidden to <li> so fixed-height rows fully collapse
- launcher/+layout.svelte: sort sessions by start_datetime (ascending) instead of name
- Rename hide_content__draft_files → show_content__internal_files (default false);
  remove redundant show_content__draft_files; rename prop hide_draft →
  show_internal_purpose_files in launcher_file_cont; update all 7 call sites and
  the menu_launcher_controls toggle. Now hides admin/draft/outline purpose files
  by default with consistent naming across the flag, prop, and toggle.

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

src/routes/events/[event_id]/(launcher)/launcher_session_view.svelte

@@ -306,6 +306,8 @@ let ae_promises: key_val = $state({});
                                     event_file_id={event_file_obj.event_file_id}
                                     {event_file_obj}
                                     hide_created_on={true}
+                                    show_internal_purpose_files={$events_loc.launcher
+                                        .show_content__internal_files}
                                     show_bak_download={$ae_loc.trusted_access &&
                                         $ae_loc.edit_mode}
                                     session_type={type_code || 'oral'}