AdaptivePing external-client scenarios cannot resolve IPingGrain

[ReubenBond]

AdaptivePing_ClientToOneSilo fails before measurement because the external client cannot resolve an implementation for BenchmarkGrainInterfaces.Ping.IPingGrain.

Reproduces on both:

• bfb902b54b9010cfe006d564ebc891e011c9d467 (perf(runtime): cache local message targets with directory entries #10886 head)
• e153535f1 (stacked callback-routing experiment)

Command:

& 'test\Benchmarks\bin\Release\net10.0\Benchmarks.exe' AdaptivePing_ClientToOneSilo

Exception:

System.ArgumentException: Could not find an implementation for interface BenchmarkGrainInterfaces.Ping.IPingGrain
   at Orleans.GrainInterfaceTypeToGrainTypeResolver.GetGrainType(...)
   at Orleans.GrainFactory.GetGrain[TGrainInterface](...)
   at Orleans.ClusterClient.GetGrain[TGrainInterface](...)
   at Benchmarks.Ping.AdaptivePingBenchmark..ctor(BenchmarkMode mode, Int32 numSilos)

The hosted-client scenario runs successfully. The external-client benchmark likely needs application-part/interface metadata configuration so the client manifest can resolve IPingGrain.