feat(matching): per-mode policy + AI-fallback branch in InProcessPairUp

InProcessPairUp now consults ModePolicyRegistry per call and reads the
fallback threshold from MatchingConfig via IServiceScopeFactory (singleton
service consuming a scoped IGameConfigService). New behavior for
PvpFirstThenAiFallback modes: when the calling viewer IS the slot's
waiter and Now - WaitingSince >= threshold, the waiter unparks and the
bridge resolves a Bot match. PvpOnly modes (TK2) keep parking forever
(modulo a 5-minute stale-waiter eviction backstop).

TimeProvider is injected so tests can drive time forward with
FakeTimeProvider — 7 new tests cover the four key transitions
(stay-parked / pair-pvp / fall-back / stale-evict) plus per-mode
isolation. Fixture uses [FixtureLifeCycle(InstancePerTestCase)] because
the assembly is Parallelizable(ParallelScope.All).

Program.cs registers ModePolicyRegistry with three rows: TK2 PvpOnly,
rotation/unlimited rank PvpFirstThenAiFallback.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.UnitTests/SVSim.UnitTests.csproj

@@ -10,6 +10,7 @@
     </PropertyGroup>
 
     <ItemGroup>
+        <PackageReference Include="Microsoft.Extensions.TimeProvider.Testing" Version="8.0.0" />
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.0" />
         <PackageReference Include="NUnit" Version="3.13.3" />
         <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />