The oauth.callback handler parsed `iss` but never passed it to deliver_callback_flow, and McpOauthCallbackParams (extra="forbid") had no `iss` field, so the desktop renderer sending `iss: null` was rejected with 4000 "unknown key" — breaking every Desktop→remote-gateway MCP OAuth login. Add the field, forward it, and regenerate the OpenRPC/TS contract artifacts via scripts/gen_gateway_contracts.py.
Also update tests/hermes_cli/test_mcp_dashboard_oauth.py for the 3-tuple callback shape introduced by the cherry-picked commit (it was red on the stack).
1c243f86de