…stered listener URIs [3/N]

Third slice of GH-2685. The previous PRs (#2699 foundation, #2700 RDBMS
storage) gave us a durable place to persist listener URIs and the
opt-in flag to gate it. This PR connects that storage to the cluster's
agent runtime so registered URIs become live listeners on exactly one
node — the user-visible API for "add an MQTT broker at runtime and
have the cluster activate it" the original issue called for.

What's in this PR:

- New `Wolverine.Runtime.Agents.DynamicListenerAgentFamily` —
  `IAgentFamily` implementation that re-reads
  `IMessageStore.Listeners.AllListenersAsync()` on every assignment
  cycle (no boot-time snapshot, so newly registered URIs are picked
  up within one polling interval, default 30s) and balances the
  resulting agents across the cluster via
  `assignments.DistributeEvenly(Scheme)`. Same pattern as the
  existing `ExclusiveListenerFamily` and
  `StickyPostgresqlQueueListenerAgentFamily`.

- New `Wolverine.Runtime.Agents.DynamicListenerAgent` — single-URI
  `IAgent` whose StartAsync resolves the listener URI's scheme to a
  registered transport via `Options.Transports.ForScheme(...)`,
  asks the transport to materialize an `Endpoint` from the URI, and
  hands it to `IEndpointCollection.StartListenerAsync`. Failure to
  resolve the transport surfaces as a hard `InvalidOperationException`
  with a hint pointing at `UseMqtt` / `UseRabbitMq` / etc., so a
  misconfigured host doesn't silently never run the listener.

- New `Wolverine.Runtime.Agents.DynamicListenerUriEncoding` — lossless
  round-trip between a listener URI and an agent URI under the
  reserved `wolverine-dynamic-listener:///` scheme (percent-encoded
  payload as the path, empty authority so embedded `://` in the
  listener URI doesn't collide with the agent URI's own parsing).
  The cluster keys agents by their URI, so the encoding has to be
  deterministic — covered by parameterized round-trip tests.

- `NodeAgentController` registers the family when both
  `Durability.Mode == Balanced` AND
  `Durability.EnableDynamicListeners == true`. Off by default;
  Solo / MediatorOnly / Serverless modes don't get cluster
  assignment so the family wouldn't help them anyway.

- New `IWolverineRuntime.RegisterListenerAsync` /
  `RemoveListenerAsync` / `AllRegisteredListenersAsync` extension
  methods in `Wolverine.Runtime.WolverineRuntimeListenerExtensions`
  so user code calls `runtime.RegisterListenerAsync(uri)` rather
  than `runtime.Storage.Listeners.RegisterListenerAsync(uri)`.
  Thin pass-through; no transformation — the public surface is just
  to keep dependency reach narrower in user code.

Tests:

- `DynamicListenerUriEncodingTests` — 6 round-trip cases covering
  MQTT topic wildcards, userinfo + port, query strings; plus
  determinism + scheme-mismatch + empty-path guards. 9/9.
- `DynamicListenerAgentFamilyTests` — verifies empty-store →
  empty agents, listener URIs project through the encoder, the
  store is re-read on every call (no caching), and BuildAgentAsync
  decodes back to a `DynamicListenerAgent`. 6/6.
- `WolverineRuntimeListenerExtensionsTests` — pins the public
  pass-through contract and argument-null guards. 7/7.
- `dynamic_listener_agent_lifecycle_integration` — spins up a real
  WolverineHost in solo mode, drives an agent through Start/Stop,
  asserts the listener actually goes live via
  `runtime.Endpoints.FindListeningAgent(uri)`. Also covers the
  no-transport error path and the "stop before start" tolerance
  needed for cluster reassignment edge cases. 3/3.

Regression checks:
- CoreTests `Runtime.Agents`: 88/88 (existing agent family suite
  plus the new 25 dynamic-listener tests).
- CoreTests `Persistence.Durability`: 17/17 (foundation defaults
  unchanged).
- PostgresqlTests `PostgresqlMessageStoreTests`: 48/48
  (RDBMS-backed listener store from PR #2700 still green).

Deferred to follow-up:
- Marten-backed `IListenerStore`.
- MQTT-specific multiplexed listener (one shared MqttListener +
  BufferedReceiver, N broker subscriptions) for the 10K-IoT case.
- IWolverineRuntime topic-name → Uri convenience extensions.
- Documentation in MQTT and Durability guides.

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