S1-b: IF-LOC v1.0 locator simulator + round-trip test

Reference implementation of the frozen IF-LOC v1.0 contract
(meta/contracts/ble-device-interface.md): byte-accurate codec for the
telemetry, capture-trigger, and capture-result frames, plus a
LocatorSimulator that replays a canned locate session over a
transport-agnostic loopback link. Unblocks App development without
firmware (Risk R-3, SRS S3.1).

Plain net9.0 (not a MAUI head) so it builds/runs headless under the QA
gate without the Android/iOS workloads; qa-gate.sh auto-discovers
*.Tests.csproj under app/tests/. Round-trip test asserts field-level
fidelity (every SRS S3.1 telemetry + capture-result field), sentinels,
endianness (incl. RFC 4122 big-endian pointId), the REJECTED path, and
exactly-once capture correlation (no silent drop, SRS-LOG-7). 8/8 green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/IfLoc.Sim.Tests/IfLoc.Sim.Tests.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <!--
+    Round-trip test for the frozen IF-LOC v1.0 contract — the mapped test for S1-b.
+    Plain net9.0 + xUnit so `dotnet test` runs headless in CI without MAUI workloads.
+    Run: dotnet test tests/IfLoc.Sim.Tests/IfLoc.Sim.Tests.csproj
+  -->
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
+    <PackageReference Include="xunit" Version="2.9.2" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\IfLoc.Sim\IfLoc.Sim.csproj" />
+  </ItemGroup>
+
+</Project>