T7-16 follow-up: live socket-auth inferenced daemon + persistent ledger + InferenceProvider reconciliation

[mdheller]

Follow-up to #124 (T7-16 slice; epic SourceOS-Linux/sourceos-spec#241). The receipt-emission mechanism is now native and tested; these are the parts beyond the buildable slice.

1. Live socket-auth inferenced daemon

The authenticated inference socket must call agent_machine.inference_receipt.emit_socket_inference_receipt() on every real completion, resolving requestingAgentRef + capabilityLeaseRef from the authenticated caller.

• AC: a real completion served over the socket produces exactly one InferenceReceipt in the ledger, carrying the caller's AgentPassport URN and the AgentCapabilityLease URN that granted the model-plane capability.
• AC: a socket call with no valid capability lease is refused before serving; no receipt is emitted (fail-closed).

2. Persistent ledger service (SEAM-011)

Today the emitter appends to a per-call file. Route emission through the estate's durable, PVC-backed ledger (receipt-gateway spine) rather than a node-local file.

• AC: receipts survive pod restart and are chained across restarts (no genesis reset per boot).
• AC: the ledger the daemon writes is the same hash-chained spine verifiable by prophet-platform apps/receipt-gateway.

3. InferenceProvider reconciliation

Agent Machine has its own contracts/inference-provider.schema.json; sourceos-spec owns the Model Carry InferenceProvider family.

• AC: a documented mapping (or a single source of truth) so providerRef on emitted receipts resolves to a real provider object without divergence.

cc @mdheller