T7-5 DECISION: add inference_provider to AgentPassport.agent_class?

[mdheller]

Part of #241 (Tranche 7). Deferred from #240 — this is a core-ontology decision, Michael's call.

Spec §VIII / §XIV T7-5 calls for adding a 6th agent_class value inference_provider to AgentPassport, amending T0-1 / ADR-0014's five-class model.

Why it wasn't done mechanically:

• The estate already models inference providers as the separate typed object InferenceProvider.json (providerClass, trustPosture, requiresNetwork, supportedModalities). This looks like a deliberate resolution that keeps the five-class host-process model intact.
• Adding a 6th class is not additive-and-free: it hard-breaks tools/validate_agent_passport_examples.py (EXPECTED_CLASSES asserts exactly the five), and must be kept in sync across schemas/AgentPassport.json (enum + description + SEAM-002 if/then list) and semantic/agent-system-vocabulary.jsonld.

Decision requested: Is the separate InferenceProvider object the accepted resolution (close T7-5), or do model-serving daemons (inferenced/visiond/…) additionally need a host-process AgentPassport class? If the latter, this needs its own ADR and the 3-place enum sync + EXPECTED_CLASSES update.