feat(stage3): scaffold task-001 baseline

- WHY: establish Stage 3 task-001 execution baseline per repo intent
- WHAT: add minimal solution/project skeleton and boundary docs
- RULE: apply stage3 execution runtime and repository workflow directives

Furniture.Service.slnx

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+<Solution>
+  <Folder Name="/src/">
+    <Project Path="src/Furniture.Service.Contracts/Furniture.Service.Contracts.csproj" />
+    <Project Path="src/Furniture.Service.Application/Furniture.Service.Application.csproj" />
+    <Project Path="src/Furniture.Service.Grpc/Furniture.Service.Grpc.csproj" />
+  </Folder>
+  <Folder Name="/tests/">
+    <Project Path="tests/Furniture.Service.Application.UnitTests/Furniture.Service.Application.UnitTests.csproj" />
+  </Folder>
+</Solution>

docs/application/use-case-boundaries.md

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+# Furniture Service Use-Case Boundaries
+
+## Orchestration Responsibilities
+
+- Application use cases orchestrate domain workflows.
+- Use cases depend on DAL-facing ports, not persistence implementations.
+- Transport handlers map to use-case contracts and do not own orchestration logic.
+
+## Current Skeleton
+
+- `IGetFurnitureAvailabilityUseCase`: orchestration boundary contract.
+- `GetFurnitureAvailabilityUseCase`: orchestration implementation.
+- `IFurnitureAvailabilityReadPort`: DAL-facing port.

docs/architecture/protocol-selection-policy.md

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+# Protocol Selection Policy
+
+## Active Protocol Rule
+
+- This service deployment uses one active protocol at a time.
+- Internal default protocol is gRPC.
+- Multi-protocol exposure is not allowed in a single deployment.
+
+## Boundary Placement
+
+- Protocol adaptation stays at BFF boundaries.
+- Service orchestration remains transport-neutral at application contracts.

docs/architecture/service-contracts.puml

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+@startuml
+skinparam packageStyle rectangle
+
+package "furniture-service" {
+  interface IGetFurnitureAvailabilityUseCase
+  class GetFurnitureAvailabilityUseCase
+  interface IFurnitureAvailabilityReadPort
+  class GetFurnitureAvailabilityRequest
+  class GetFurnitureAvailabilityResponse
+
+  GetFurnitureAvailabilityUseCase ..|> IGetFurnitureAvailabilityUseCase
+  GetFurnitureAvailabilityUseCase --> IFurnitureAvailabilityReadPort
+  IGetFurnitureAvailabilityUseCase --> GetFurnitureAvailabilityRequest
+  IGetFurnitureAvailabilityUseCase --> GetFurnitureAvailabilityResponse
+}
+
+package "furniture-bff" as FurnitureBff
+package "furniture-dal" as FurnitureDal
+
+FurnitureBff --> IGetFurnitureAvailabilityUseCase
+GetFurnitureAvailabilityUseCase --> IFurnitureAvailabilityReadPort
+IFurnitureAvailabilityReadPort ..> FurnitureDal
+@enduml

src/Furniture.Service.Application/Furniture.Service.Application.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\Furniture.Service.Contracts\Furniture.Service.Contracts.csproj" />
+  </ItemGroup>
+</Project>

src/Furniture.Service.Application/Ports/IFurnitureAvailabilityReadPort.cs

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+using Furniture.Service.Contracts.UseCases;
+
+namespace Furniture.Service.Application.Ports;
+
+/// <summary>
+/// Defines DAL-facing read port for furniture availability.
+/// </summary>
+public interface IFurnitureAvailabilityReadPort
+{
+    /// <summary>
+    /// Retrieves current availability for a furniture aggregate.
+    /// </summary>
+    /// <param name="furnitureId">Furniture aggregate identifier.</param>
+    /// <returns>Availability response contract.</returns>
+    Task<GetFurnitureAvailabilityResponse> GetAvailabilityAsync(string furnitureId);
+}

src/Furniture.Service.Application/UseCases/GetFurnitureAvailabilityUseCase.cs

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+using Furniture.Service.Application.Ports;
+using Furniture.Service.Contracts.UseCases;
+
+namespace Furniture.Service.Application.UseCases;
+
+/// <summary>
+/// Default orchestration implementation for furniture availability lookup.
+/// </summary>
+public sealed class GetFurnitureAvailabilityUseCase(IFurnitureAvailabilityReadPort readPort)
+    : IGetFurnitureAvailabilityUseCase
+{
+    /// <inheritdoc />
+    public Task<GetFurnitureAvailabilityResponse> HandleAsync(GetFurnitureAvailabilityRequest request)
+    {
+        return readPort.GetAvailabilityAsync(request.FurnitureId);
+    }
+}

src/Furniture.Service.Application/UseCases/IGetFurnitureAvailabilityUseCase.cs

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+using Furniture.Service.Contracts.UseCases;
+
+namespace Furniture.Service.Application.UseCases;
+
+/// <summary>
+/// Defines orchestration boundary for furniture availability lookup.
+/// </summary>
+public interface IGetFurnitureAvailabilityUseCase
+{
+    /// <summary>
+    /// Handles the availability lookup use case.
+    /// </summary>
+    /// <param name="request">Use-case request contract.</param>
+    /// <returns>Use-case response contract.</returns>
+    Task<GetFurnitureAvailabilityResponse> HandleAsync(GetFurnitureAvailabilityRequest request);
+}

src/Furniture.Service.Contracts/Furniture.Service.Contracts.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+</Project>

src/Furniture.Service.Contracts/UseCases/GetFurnitureAvailabilityRequest.cs

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+namespace Furniture.Service.Contracts.UseCases;
+
+/// <summary>
+/// Request contract for furniture availability lookup.
+/// </summary>
+/// <param name="FurnitureId">Furniture aggregate identifier.</param>
+public sealed record GetFurnitureAvailabilityRequest(string FurnitureId);

src/Furniture.Service.Contracts/UseCases/GetFurnitureAvailabilityResponse.cs

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+namespace Furniture.Service.Contracts.UseCases;
+
+/// <summary>
+/// Response contract for furniture availability lookup.
+/// </summary>
+/// <param name="FurnitureId">Furniture aggregate identifier.</param>
+/// <param name="QuantityAvailable">Available quantity for the requested furniture.</param>
+public sealed record GetFurnitureAvailabilityResponse(string FurnitureId, int QuantityAvailable);

src/Furniture.Service.Grpc/Furniture.Service.Grpc.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\Furniture.Service.Application\Furniture.Service.Application.csproj" />
+    <ProjectReference Include="..\Furniture.Service.Contracts\Furniture.Service.Contracts.csproj" />
+  </ItemGroup>
+</Project>

src/Furniture.Service.Grpc/Program.cs

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+var builder = WebApplication.CreateBuilder(args);
+
+// Stage 3 skeleton: keep a single active internal protocol policy (gRPC-first).
+var app = builder.Build();
+
+app.Run();

tests/Furniture.Service.Application.UnitTests/Furniture.Service.Application.UnitTests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Furniture.Service.Application\Furniture.Service.Application.csproj" />
+    <ProjectReference Include="..\..\src\Furniture.Service.Contracts\Furniture.Service.Contracts.csproj" />
+  </ItemGroup>
+</Project>

tests/Furniture.Service.Application.UnitTests/GetFurnitureAvailabilityUseCaseTests.cs

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+using Furniture.Service.Application.Ports;
+using Furniture.Service.Application.UseCases;
+using Furniture.Service.Contracts.UseCases;
+
+namespace Furniture.Service.Application.UnitTests;
+
+public class GetFurnitureAvailabilityUseCaseTests
+{
+    [Fact]
+    public async Task HandleAsync_WhenCalled_DelegatesToReadPort()
+    {
+        var port = new FakeFurnitureAvailabilityReadPort();
+        var useCase = new GetFurnitureAvailabilityUseCase(port);
+
+        var response = await useCase.HandleAsync(new GetFurnitureAvailabilityRequest("FUR-001"));
+
+        Assert.Equal("FUR-001", response.FurnitureId);
+        Assert.Equal(10, response.QuantityAvailable);
+    }
+
+    private sealed class FakeFurnitureAvailabilityReadPort : IFurnitureAvailabilityReadPort
+    {
+        public Task<GetFurnitureAvailabilityResponse> GetAvailabilityAsync(string furnitureId)
+        {
+            return Task.FromResult(new GetFurnitureAvailabilityResponse(furnitureId, 10));
+        }
+    }
+}