v2026.10.09 — structure members, flat and addressable

The follow-ups to the hidden-members work of v2026.10.08, verified against a live BW system on the SAP
NetWeaver SDK and the erpl-proto backend.

Added

• [bics] sap_bics_structure_members(query | cube, query | id => state): one row per structure member of a
  BEx query (structure, structure_technical_name, structure_text, structure_kind, element_uid, text,
  technical_name, position, visibility, in_selection), the flat form of the structures lists in
  sap_bics_describe (#164).
• [bics] Structure members in sap_bics_describe and in the DESCRIBE return of the session functions carry
  in_selection: whether an include/equal entry of the structure's current selection selects the member, so the
  effect of sap_bics_hidden_members and sap_bics_filter is visible without a result fetch. true for every
  member of a selection without entries (BW shows all then); a selection holding only exclusions or ranges
  selects nothing; NULL in the design-time (cube, query) form (#163).

Fixed

• [bics] A structure given by the technical name the query designer assigned to it is accepted by
  sap_bics_hidden_members and sap_bics_filter alike; BW reports that name as the structure's alternative name
  while its selection state keeps the element uid. Covered by the ZERPL_Q154_KF fixture (#165).