feat(java-client): CLI-15 ReplayGap surface + CLI-04 typed-command parity (5/5 complete)

Completes both findings across all five clients — done locally on the Mac now
that homebrew openjdk@17 is available (JAVA_HOME=/opt/homebrew/opt/openjdk@17).

CLI-15: new MxEventStreamItem record + MxEventStream.nextItem() surfaces the
gateway's ReplayGap sentinel as a typed, non-terminal signal (isReplayGap()/
replayGap()/event()); existing Iterator<MxEvent> path unchanged, sentinel never
swallowed/synthesized. Javadoc covers gap semantics + resume contract.

CLI-04: typed single-item helpers on MxGatewaySession — Phase 1
adviseSupervisory/writeSecured/writeSecured2/authenticateUser/archestrAUserToId,
Phase 2 addBufferedItem/setBufferedUpdateInterval/suspend/activate (unregister
already present). Each routes through invokeCommand -> ensureProtocolSuccess +
ensureMxAccessSuccess (same validation as bulk). MXAccess parity preserved.
Credentials flow only into the request proto; exceptions carry only the reply and
gRPC status text is scrubbed via MxGatewaySecrets.redactCredentials — tests
assert the password/secured value is absent from getMessage()/toString()/CLI
output. New CLI subcommands write-secured/authenticate-user (credential via
--password/--password-env, prints only the user id).

gradle test: 106 tests, 0 failures (58 client + 48 cli); no generated churn.
Shared docs: ClientLibrariesDesign + CLAUDE.md updated to "all five clients".

Claude-Session: https://claude.ai/code/session_01DMXXvNuPekkkrTEyPNxEkW

CLAUDE.md

@@ -76,7 +76,7 @@ powershell -ExecutionPolicy Bypass -File scripts/run-client-e2e-tests.ps1
 - **Style guides** in `docs/style-guides/` are authoritative. Follow `CSharpStyleGuide.md` for gateway/worker/.NET-client code: file-scoped namespaces, `sealed` by default, `Async` suffix on Task-returning methods, MXAccess-aligned names (`MxStatusProxy`, `ServerHandle`, `ItemHandle`, `HResult`).
 - **MXAccess parity is the contract.** Don't "fix" surprising MXAccess behavior (e.g., `WriteSecured` failing before a value-bearing NMX body, distinct `OperationComplete` semantics, invalid-handle exceptions) unless the client explicitly opts into a non-parity mode. The installed MXAccess COM component is the baseline.
 - **Don't synthesize events.** The gateway forwards only events the worker emits; it never invents `OperationComplete` from write completion or command replies.
-- **One worker per session** (invariant). Multi-subscriber event fan-out and reconnect-with-replay have shipped and are config-gated: `AllowMultipleEventSubscribers` (default `false`) enables fan-out up to `MaxEventSubscribersPerSession` (default `8`); `DetachGraceSeconds` (default `30`) retains a session after its last subscriber drops so clients can reconnect; `ReplayBufferCapacity` / `ReplayRetentionSeconds` control how much event history the replay ring keeps. Default config is single-subscriber (`AllowMultipleEventSubscribers` off), but detach-grace and replay retention are **on** by default (`DetachGraceSeconds=30`, `ReplayBufferCapacity=1024`, `ReplayRetentionSeconds=300`): a detached session is retained for 30 s and recent events are buffered for reconnect. The reconnect protocol is consumable end-to-end: a resuming `StreamEvents` (via `after_worker_sequence`) that predates the retained ring gets a `ReplayGap` sentinel, and the official clients surface it as a typed signal (shipped for .NET/Go/Rust/Python; the Java client is the remaining one, batched to windev). Orphan-worker reattach after a gateway restart is **deferred, not planned** — see `oldtasks.md` (session-resilience epic Phase 5); the invariant on the next line stands. See `docs/DesignDecisions.md` and `docs/Sessions.md`.
+- **One worker per session** (invariant). Multi-subscriber event fan-out and reconnect-with-replay have shipped and are config-gated: `AllowMultipleEventSubscribers` (default `false`) enables fan-out up to `MaxEventSubscribersPerSession` (default `8`); `DetachGraceSeconds` (default `30`) retains a session after its last subscriber drops so clients can reconnect; `ReplayBufferCapacity` / `ReplayRetentionSeconds` control how much event history the replay ring keeps. Default config is single-subscriber (`AllowMultipleEventSubscribers` off), but detach-grace and replay retention are **on** by default (`DetachGraceSeconds=30`, `ReplayBufferCapacity=1024`, `ReplayRetentionSeconds=300`): a detached session is retained for 30 s and recent events are buffered for reconnect. The reconnect protocol is consumable end-to-end: a resuming `StreamEvents` (via `after_worker_sequence`) that predates the retained ring gets a `ReplayGap` sentinel, and all five official clients surface it as a typed signal. Orphan-worker reattach after a gateway restart is **deferred, not planned** — see `oldtasks.md` (session-resilience epic Phase 5); the invariant on the next line stands. See `docs/DesignDecisions.md` and `docs/Sessions.md`.
 - **Gateway restart does not reattach orphan workers.** The first version terminates orphaned workers on startup; do not design code paths that assume reattachment.
 - **No Blazor UI component libraries.** Dashboard uses local Bootstrap CSS/JS only — do not introduce MudBlazor, Radzen, FluentUI, etc.
 - **Don't log secrets or full tag values by default.** API keys, passwords, `WriteSecured` payloads, and `AuthenticateUser` credentials must never reach logs. Value logging is opt-in and redacted.