CLPR-1.6: Endpoint roster update via state proof — OBSOLETE

## ⚠️ This issue is OBSOLETE

The `updateEndpointRoster` transaction and on-chain peer endpoint rosters have been removed from the CLPR specification.

**Why:** Propagating endpoint roster changes across N connections via on-chain state is prohibitively expensive. On Ethereum with 1000 endpoints and 1000 connections, a single endpoint change would cost ~$25K in gas.

**New design:** Peer endpoint discovery is handled entirely off-chain via gossip between endpoints:
- Seed endpoints (up to 10) are included in `ClprLedgerConfiguration` and propagated via `ConfigUpdate`
- Endpoints discover additional peers via the `discoverEndpoints` gRPC RPC
- Peer endpoint data is NOT stored in on-ledger state
- No `verifyEndpoints()` on the verifier interface
- No `EndpointJoin`/`EndpointLeave` control messages

See cross-platform spec §5.4 for the new endpoint discovery model.

The issue is explicitly marked OBSOLETE, and the former updateEndpointRoster transaction and endpoint-roster state were removed from the specification. Read cross-platform spec §5.4 only to understand the replacement discovery model; there is no implementation change or completion test identified here.

Written by the indexing model from the issue text.