refactor(geode): rename relay classes for clarity, move test helpers off public API

Renames in the geode module to make naming honest:
- Relay -> RelayEngine (the transport-agnostic core)
- LocalRelayServer -> KtorRelay (Ktor/CIO transport; defaults to 127.0.0.1
  but supports public deployment, so "Local" was misleading)
- RelayHub -> InProcessRelays (URL-keyed registry that doubles as a
  WebsocketBuilder for in-JVM tests; "Hub"/"Pool" implied substitutable
  resources, but each URL maps to a distinct relay)

Also moves the test-only helpers `preload` and `publish` out of
RelayEngine and into a testFixtures extension file. As part of that,
`publish` now waits for the relay's OK reply before returning so that
publish-then-subscribe is deterministic — previously the fire-and-forget
submit let a subscription register after publish returned but before the
ingest queue fanned out, causing ephemeral kinds (not persisted) to leak
to late subscribers. Fixes the flaky
`Nip01ComplianceTest.ephemeralEventIsNotStoredAndDoesNotShowOnFollowupReq`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

geode/plans/2026-05-07-connection-scaling.md

@@ -95,7 +95,7 @@ path = "/"
 
 Default is **`null` (Ktor default)** — no behavior change unless an
 operator explicitly tunes them. The values are wired through
-`LocalRelayServer` into the new `embeddedServer(factory = CIO,
+`KtorRelay` into the new `embeddedServer(factory = CIO,
 rootConfig = serverConfig {…}, configure = {…})` overload (the
 short-form `embeddedServer(factory, host, port) {…}` overload doesn't
 expose CIO config). The auto-connector that the short form created

geode/plans/2026-05-07-event-ingestion-batching.md

@@ -93,7 +93,7 @@ on each batch before opening the SQLite transaction. Failed
 verifies pre-mark `Rejected` and skip the insert.
 
 Wired through `NostrServer(parallelVerify = ...)` and
-`geode.Relay(parallelVerify = ...)`, controlled by
+`geode.RelayEngine(parallelVerify = ...)`, controlled by
 `[options].parallel_verify` in the relay config (default `true`)
 and `--no-parallel-verify` on the CLI. Internal direct callers of
 `NostrServer` (tests, library users) are opt-in: the flag defaults