[#4454 Phase 1D] Reflection-driven CompiledQueryHandlerDescriptor fallback

[jeremydmiller]

Summary

Phase 1D of #4454. When CompiledQueryHandlerRegistry.TryGet(queryType) misses — the consumer's assembly is missing the [JasperFxAssembly] marker that Marten.SourceGenerator needs, or the query type was registered at runtime via reflection — we now build the descriptor reflectively from the freshly walked CompiledQueryPlan instead of falling through to CompiledQuerySourceBuilder / JasperFx.RuntimeCompiler. The constructed descriptor is registered with CompiledQueryHandlerRegistry so subsequent session.Query(compiledQuery) invocations hit the fast registry path — descriptor build cost is paid once per query type, never per row.

After this PR, the Roslyn-emit codegen path (CompiledQuerySourceBuilder, CompiledQueryCodeFile, StatelessCompiledQuery / ClonedCompiledQuery / ComplexCompiledQuery base classes) is runtime-unreachable for the live query dispatch path. Phase 1E deletes the dead code; only BuildFiles()'s codegen surface for the dotnet marten codegen ... CLI remains, and Phase 5 retires that.

(Phase 1C — "finish the source generator" — was already covered by the in-tree CompiledQuerySourceGenerator's iteration-2/3 emit. The generator already discovers ICompiledQuery<TDoc, TOut> implementations in [JasperFxAssembly]-marked assemblies and emits a [ModuleInitializer] per type that registers a CompiledQueryHandlerDescriptor. This PR closes the runtime side of 1C+1D — the fallback when the generator hasn't run.)

What's in RuntimeCompiledQueryDescriptorFactory

Mirrors the source generator's emit:

• BindParameter — a per-queryType dictionary of per-member binders. Each binder knows the NpgsqlDbType + read strategy for one parameter member (scalar / array / enum / byte[]). EnumStorage branches inline on the enumAsString flag the descriptor caller passes, so a single descriptor serves stores with mixed enum-storage configs.
• AttachIncludeReaders — dispatches by the include member's declared type (Action<T>, IList<T> / List<T>, IDictionary<TId, T> / Dictionary<TId, T>) onto Include.ReaderToAction<T> / ReaderToList<T> / ReaderToDictionary<T, TId> via MakeGenericMethod. One MakeGenericMethod call per include member per session.Query(...) — cheap relative to the SQL round-trip that follows.
• ReadStatistics — direct MemberInfo.GetValue read against the StatisticsMember captured on the plan, or null when the query has no statistics member.

DocType is resolved from the query type's ICompiledQuery<TDoc, TOut> generic arguments via reflection (covers ICompiledListQuery and any future shape extensions because they all extend ICompiledQuery<,>).

The factory carries [RequiresUnreferencedCode] + [RequiresDynamicCode] so AOT publishers see the right warning at the boundary. #4454 Phase 5's AOT-compliance pass decides whether this fallback survives long-term or gets replaced behind those annotations with a source-gen-only contract.

Call-site collapse

DocumentStore.CompiledQueryCollection's registry-miss path collapses to:

if (!CompiledQueryHandlerRegistry.TryGet(query.GetType(), out var descriptor))
{
    descriptor = RuntimeCompiledQueryDescriptorFactory.Build(plan);
    CompiledQueryHandlerRegistry.Register(query.GetType(), descriptor);
}
// ... hand to SourceGeneratedCompiledQuerySource<TOut> ...

22-line block replacing the prior CompiledQueryCodeFile + Roslyn-emit fallthrough.

Verification

dotnet test src/CompiledQueryTests/CompiledQueryTests.csproj
→ 9/9 pass

dotnet test src/LinqTests/LinqTests.csproj
→ 1257/1258 pass (one unrelated skip carried over from master)

Follow-up phases

• 1E — delete the now-unreachable codegen path (CompiledQuerySourceBuilder, CompiledQueryCodeFile, the three codegen-emitted handler base classes, the GenerateCode method on ICompiledQueryAwareFilter).
• 2 — flip event-store closed-shape to the default + delete the extra closed-shape GH Action profiles.
• 3 — port ancillary stores to the closed-shape provider.
• 4 — daemon / projection codegen audit.
• 5 — remove JasperFx.RuntimeCompiler PackageReference + retire dotnet marten codegen ... CLI verbs. That's the "Boom" PR.

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