feat(tests): standalone .NET dispatch test (closes #11)

[Taure]

Why

smoke.yml uses game-ci/unity-test-runner@v4 which needs UNITY_LICENSE / UNITY_EMAIL / UNITY_PASSWORD secrets to compile + run anything (#11). Those secrets aren't provisioned, so neither the existing PlayMode smoke nor the 32-fixture protocol dispatch test added in #12 can act as a required check today.

This is the same problem the Unreal SDK had. We solved it there by extracting the engine-agnostic C++ into a CMake static lib + doctest exe (Source/AsobiCore/) that runs on stock ubuntu-24.04. This PR is the C# equivalent for asobi-unity.

What

A standalone dotnet test project that exercises the same dispatch logic Unity runs, with zero Unity dependencies.

Refactor (decision: extract pure protocol code)

Runtime/WebSocket/AsobiDispatcher.cs — new pure-C# base class that owns:

• All On* event declarations (35 events)
• HandleMessage(raw) — the dispatch switch
• ProtocolEnvelope.Parse(raw) — a tiny zero-dep parser that pulls just type and cid from the envelope (replaces the Unity-only JsonUtility.FromJson<WsMessage> in the dispatch path)

AsobiRealtime now : AsobiDispatcher — only retains the Unity-aware concerns (ClientWebSocket, JsonUtility payload serialization, async send/receive). Cid resolution stays on the subclass via an OnPendingResponse virtual hook.

No public API changes — the events stay where consumers see them on AsobiRealtime (inherited).

Standalone .NET test project

Tests/AsobiCore.NET/:

• Asobi.Core.Tests.csproj — net8.0, NUnit 4 (matches the existing Unity test asmdef which uses NUnit attributes)
• <Compile Include="..\..\Runtime\WebSocket\AsobiDispatcher.cs" Link="..."/> — shared source, no copies
• <None Include="..\..\Tests\Runtime\Resources\Fixtures\*.json" CopyToOutputDirectory="PreserveNewest" /> — same 32 fixtures Unity loads via Resources.LoadAll<TextAsset>, here loaded from AppContext.BaseDirectory/Fixtures/
• DispatcherTests.cs — port of Tests/Runtime/DispatchTests.cs (from feat(tests): protocol dispatch test against canonical fixtures #12), targeting AsobiDispatcher directly

Tests/AsobiCore.NET/ also has an asmdef gated on a never-set defineConstraints so Unity's predefined assembly never picks up DispatcherTests.cs.

What it tests

• 32 fixture cases (one [Test] per fixture via [TestCaseSource])
• EveryFixtureHasExpectedMapping / EveryExpectedHasFixture — pin the bijection between fixture set and dispatch switch
• MatchmakerMatchedAliasesMatchMatched — pins the matchmaker.matched -> match.matched historical alias

Total tests: 35
     Passed: 35
 Total time: 0.79 Seconds

CI

.github/workflows/dispatch.yml — new job on ubuntu-24.04, just setup-dotnet + dotnet test. No secrets. This is the new required check for protocol regressions. The existing smoke.yml stays so the PlayMode test runs once #11's secrets land.

SmokeTest.cs fixes

The file shipped with #8 had compile errors (called .match_id on string event payloads, used non-existent SendMatchInput / Disconnect APIs) that didn't show up because the Unity job never compiled them. Fixed in a separate commit:

• Read match_id via JsonHelper.ExtractJsonField on the raw event JSON
• SendMatchInput -> SendMatchInputAsync
• Disconnect -> DisconnectAsync

Coordination with #12

Per repo convention, kept #12's Unity-side test alongside this one (option (a) in the brief). This PR cherry-picks #12's commit so the dispatcher refactor can build on the events #12 introduced (OnHeartbeat, OnMatchFinished, etc.). When either PR merges first, the other rebases cleanly — git detects the identical commit. The .NET test in this PR becomes the required check; the PlayMode test stays for when secrets land.

Test plan

• dotnet test Tests/AsobiCore.NET/Asobi.Core.Tests.csproj — 35/35 green locally
• CI dispatch.yml passes on ubuntu-24.04 with no secrets
• Verify Unity asmdef still compiles (manual — no license to run locally; review the diff for import breakage)

Closes #11.

Do not merge — leave for morning review.