v0.9.0

Changed

• BREAKING (pkg/litefake): heating groups answer members the way
  an openccu-lite box does. members, former_members and
  devices_to_configure are objects ({id, serial, type}) instead of
  bare ids; a create and an update answer the group's detail plus the
  members as devices_to_configure; the detail carries
  device_name as <name> <device>, every offered type as
  {id, label} and no type_label; the type labels are the box's
  (Heating_Control, HmIP-Heizungssteuerung). The candidates of a
  group type are seeded with the new Options.GroupCandidates; a
  member that is no candidate is dropped without an error, as on a
  box, and a channel that belongs to a group is listed as leftover.
  A test that created a group with an arbitrary member id now has to
  seed that id as a candidate. Read and written on a box on
  2026-10-03; CONTRACT.md records the observations.

• Requires Go 1.27.1. go.mod targets Go 1.27.1 and CI and release
  builds use it, the same patch release openccu-loom builds with.