Add StreamOne/StreamMany/StreamAggregate typed streaming result types

[jeremydmiller]

Summary

Marten.AspNetCore already ships WriteSingle / WriteArray / WriteLatest extension helpers that stream raw JSON directly to an HttpResponse. This PR adds three typed endpoint return values that wrap that behavior for Minimal API endpoints (and any framework that dispatches IResult, e.g. Wolverine.Http).

Type	Source	Response shape	404 on miss?
StreamOne<T>	IQueryable<T> — regular Marten document query	Single T	yes
StreamMany<T>	IQueryable<T> — regular Marten document query	JSON array T[]	no (empty [])
StreamAggregate<T>	IDocumentSession + stream id — event-sourced	Single T	yes

Why

WriteSingle(HttpContext) / WriteArray(HttpContext) / WriteLatest(HttpContext) are already great at what they do, but endpoint authors have to manually wire the result up and lose typed return values (and therefore lose good OpenAPI metadata). These wrappers give Minimal API and Wolverine.Http users a concise, typed alternative that still gets raw-JSON-from-the-database streaming.

Design

• Each type implements both IResult (so ASP.NET Minimal API dispatches it via ExecuteAsync) and IEndpointMetadataProvider (so Swashbuckle, NSwag, and the built-in OpenAPI generator see the right response shape — Produces<T> / Produces<IReadOnlyList<T>> / Produces(404)).
• ExecuteAsync delegates to the existing extension helpers — zero behavioral drift.
• OnFoundStatus (default 200) and ContentType (default application/json) are init-only properties so endpoints can customize e.g. 201 Created or a vendor-specific content type.
• StreamAggregate<T> requires IDocumentSession (mirroring the existing WriteLatest constraint).

Example

```csharp
app.MapGet("/issues/{id:guid}",
(Guid id, IQuerySession session) =>
new StreamOne(session.Query().Where(x => x.Id == id)));

app.MapGet("/issues/open",
(IQuerySession session) =>
new StreamMany(session.Query().Where(x => x.Open)));

app.MapGet("/orders/{id:guid}",
(Guid id, IDocumentSession session) =>
new StreamAggregate(session, id));
```

Scope

• New files: `StreamOne.cs`, `StreamMany.cs`, `StreamAggregate.cs` in `Marten.AspNetCore`
• IssueService now also maps Minimal-API endpoints under `/minimal/...` so the test host exercises both controllers and Minimal API
• 12 new tests in `Marten.AspNetCore.Testing/streaming_result_types_tests.cs` covering: hit/miss, custom status code, custom content type, empty-array behavior, aggregate with 404, OpenAPI metadata assertions
• Docs: new "Typed Streaming Result Types" section in `docs/documents/aspnetcore.md` with the StreamOne-vs-StreamAggregate distinction called out

Test plan

• 12 new Alba-driven Minimal-API tests pass
• All 40 existing `Marten.AspNetCore.Testing` tests still pass

🤖 Generated with Claude Code