Add scheduled delivery to the Mocha in-memory transport

[glen-84]

Summary

• The Mocha in-memory transport now supports scheduled delivery out of the box: a message dispatched with a ScheduledTime (via ScheduleSendAsync/SchedulePublishAsync, or a saga's descriptor.Timeout(...)) is delivered at ~that time instead of immediately, and can be cancelled via the returned token. AddInMemory() registers a transport-scoped store plus a hosted delivery worker on the post-Rework scheduling #10036 ScheduledMessageStoreRegistration/resolver model. Delivery is in-process, non-durable (scheduled messages are lost on restart), and best-effort (no retry).
• The worker owns a dedicated ISchedulerSignal rather than the shared singleton, because MessageBusSchedulerSignal is a single-waiter primitive (two workers on one instance would corrupt each other's wait). Hardening that signal's notify/wait handshake against lost wake-ups (notify-before-wait and stale-target-between-waits) also benefits the Postgres dispatcher, which shares the type.
• Mocha.EntityFrameworkCore.Postgres.Tests scheduling tests are re-pointed onto a bare in-memory transport so they still exercise the EF UsePostgresScheduling() fallback: with in-memory now having native scheduling, the previous "in-memory transport + EF fallback" pairing is obsolete. Docs updated: in-memory scheduling is native, on by default, cancellable, and non-durable, with Postgres-specific troubleshooting scoped accordingly.

Test plan

• New in-memory scheduling suites (store unit tests + end-to-end with FakeTimeProvider): not-delivered-before-due, delivered-after-due, cancellation prevents delivery, body/headers preserved across pooled-context reuse, same-due-time ordering.
• Scheduler-signal race tests (notify-before-wait, stale-target-between-waits) added red→green.
• Saga timeout integration test updated for real deferred scheduling.
• Verified locally, all green: InMemory 844, Mocha.Tests 3940, Sagas 568 pass/4 skip, Mocha.EntityFrameworkCore.Postgres.Tests scheduling 52 (Squadron/Docker).

[github-actions]

Patch coverage

80.4% of changed lines covered (197/245)

File	Covered	Changed	Patch %
…/Scheduling/InMemoryScheduledMessageWorker.cs	84	122	68.9% 🔴
…/Scheduling/InMemoryTransportScheduledMessageStore.cs	73	83	88.0% 🟡
…/src/Mocha.Transport.InMemory/MessageBusBuilderExtensions.cs	18	18	100.0% 🟢
src/Mocha/src/Mocha/Scheduling/MessageBusSchedulerSignal.cs	22	22	100.0% 🟢

Uncovered changed lines (JSON)

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Project coverage: 53.7% (231047/429857 lines)

[Copilot]

Pull request overview

Adds native (non-durable) scheduled delivery support to Mocha’s in-memory transport, including a transport-owned in-process store + hosted delivery worker, plus scheduler-signal race hardening and documentation/test updates to reflect the new default behavior.

Changes:

• Implement in-memory scheduled message store + hosted worker, wired up automatically via AddInMemory().
• Harden MessageBusSchedulerSignal against notify/wait races; add regression tests.
• Re-point Postgres EF fallback scheduling tests and update docs to reflect in-memory native scheduling and behavior differences.

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
website/content/docs/mocha/transports/index.md	Updates transport decision matrix to reflect native in-memory scheduling.
website/content/docs/mocha/transports/in-memory.md	Documents in-memory scheduled delivery, cancellation, and non-durability.
website/content/docs/mocha/scheduling.md	Updates scheduling docs for in-memory native store and retry/troubleshooting distinctions.
website/content/docs/mocha/sagas.md	Updates saga timeout prerequisites to include in-memory native scheduling.
src/Mocha/test/Mocha.Transport.InMemory.Tests/Scheduling/InMemoryTransportScheduledMessageStoreTests.cs	Adds unit tests for the new in-memory scheduled message store behavior.
src/Mocha/test/Mocha.Transport.InMemory.Tests/Scheduling/InMemorySchedulingTests.cs	Adds end-to-end scheduled delivery tests using FakeTimeProvider.
src/Mocha/test/Mocha.Transport.InMemory.Tests/Mocha.Transport.InMemory.Tests.csproj	Adds Microsoft.Extensions.TimeProvider.Testing package for FakeTimeProvider.
src/Mocha/test/Mocha.Transport.InMemory.Tests/Helpers/MessageBusBuilder.cs	Starts hosted services in test helper so scheduled worker runs during tests.
src/Mocha/test/Mocha.Tests/Scheduling/SchedulingMiddlewareIntegrationTests.cs	Updates integration tests to use an in-memory transport without native scheduling registration when testing “no store” behavior.
src/Mocha/test/Mocha.Tests/Scheduling/MessageBusSchedulerSignalTests.cs	Adds regression tests for notify-before-wait and stale-target scenarios.
src/Mocha/test/Mocha.Sagas.Tests/IntegrationTests.cs	Removes custom test scheduled store registration now that in-memory has native scheduling.
src/Mocha/test/Mocha.EntityFrameworkCore.Postgres.Tests/PostgresSchedulingIntegrationTests.cs	Ensures EF Core Postgres fallback scheduling remains exercised by using an in-memory transport without native scheduling store.
src/Mocha/src/Mocha/Scheduling/MessageBusSchedulerSignal.cs	Implements lost-wakeup hardening for scheduler signal notify/wait handshake.
src/Mocha/src/Mocha.Transport.InMemory/Scheduling/InMemoryTransportScheduledMessageStore.cs	Introduces in-memory scheduled message store with ordering + cancellation + dedicated signal.
src/Mocha/src/Mocha.Transport.InMemory/Scheduling/InMemoryScheduledMessageWorker.cs	Adds hosted worker that dispatches due scheduled messages via normal dispatch pipeline.
src/Mocha/src/Mocha.Transport.InMemory/Mocha.Transport.InMemory.csproj	Adds Mocha.Outbox reference needed by the scheduled dispatch worker.
src/Mocha/src/Mocha.Transport.InMemory/MessageBusBuilderExtensions.cs	Wires in-memory scheduled store + worker into AddInMemory() by default.

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