v0.16.0

Changed

• SERVICE_SPECS now uses SpecCapability instead of a bare SpecToolset.
  The exposed tool set is byte-identical, but the spec path
  is now a Pydantic-AI capability on AgentConfig.capabilities, so it also
  teaches the model SpecToolset's conventions — that list tools accept
  page / limit / order, and the error contract (an {"error": …} result is
  a final answer, a retry message means fix the argument, a permission error is
  final) — via instructions appended to the system prompt, closing the gap where
  the model rediscovered them by failing a call. Requires
  djangorestframework-pydantic-ai>=0.5 (the [spec-tools] extra pin moves from
  >=0.2,<0.4 to >=0.5,<0.6). Name-collision precedence, the tool-card catalog,
  and the per-request user binding are unchanged. The internal
  django_ag_ui.integrations.build_spec_toolset helper is replaced by
  build_spec_capability (not a public export).