Adopt the lifted JasperFx.Events ProjectionScenario

[jeremydmiller]

Follow-up to #5127 / #5132. Consumes the cross-store lift in JasperFx/jasperfx#616.

Important

Draft: this will not go green until JasperFx.Events 2.38.0 is published. The Directory.Packages.props pin here is the intended published version — #616 is open, not merged. The branch was built and tested against a local pack of that branch; it needs re-verification against the real package before this leaves draft.

What changes

Marten's Events/TestSupport goes from seven files of harness to a single ~70-line subclass. Everything about how a scenario behaves — step queueing, batched commits, the #5126 trailing flush, action fail-fast, the re-execution guard, daemon lifecycle, Timeout — now lives on the shared ProjectionScenario<TOperations, TQuerySession> base type in JasperFx.Events.TestSupport.

What's left in Marten is only the store-specific seam: DeleteExistingDataAsync, HasAnyAsyncProjections, BuildDaemonAsync, OpenSession, SaveChangesAsync, EventsFor, and the object-id LoadDocumentAsync dispatch — the same switch MartenComplianceFixture already carries. Net −692 / +51 lines.

API impact

Small, and on top of the already-breaking #5132:

• scenario.Execute(ct) → scenario.ExecuteAsync(ct).
• ProjectionScenarioException and ProjectionScenarioAssertionException move from Marten.Events.TestSupport to JasperFx.Events.TestSupport. Test code that catches either needs the new using.
• DocumentShouldExist<T> / DocumentShouldNotExist<T> now take object ids on the base type instead of four typed overloads each. Existing typed call sites keep compiling — everything converts to object.

Everything else a user touches is unchanged from #5132.

Verification (against a local pack of #616)

• Marten.slnx builds clean.
• DaemonTests scenario suite 15/15 on net9.0 — the 8 original tests, the 2 from ProjectionScenario silently drops a trailing append — the events are never committed #5126, and the 5 from ProjectionScenario ergonomics and quality pass #5132, all unmodified apart from the ExecuteAsync rename and the exception using.
• CoreTests exception convention test green.

Merge order

1. Not possible to use Serializable transactions #616 merges and JasperFx.Events 2.38.0 publishes.
2. Re-verify this branch against the real package, undraft.
3. Consume the lifted JasperFx.Events ProjectionScenario polecat#404 then subclasses the same base type — no hand-ported overloads.

🤖 Generated with Claude Code

[jeremydmiller]

Rebased onto master now that JasperFx.Events 2.38.0 is published and #5135 has landed. The Directory.Packages.props pin edit dropped out as redundant — master already carries 2.38.0.

Re-verified against the published package rather than the local pack this was originally proven with: full Marten.slnx builds clean and the scenario suite is 15/15 on net9.0. Out of draft.

🤖 Generated with Claude Code