[SunSi12138]

Summary

• route session activity, heartbeat, reconnect, retry, breaker, admission, dynamic drain, multi-cluster retirement, and server shutdown timing through each runtime context's TimeProvider
• add overflow-safe monotonic deadline helpers, provider-aware wait paths, and a reconnect-only deterministic jitter seam without changing the wire protocol
• preserve LastActive as simple UTC diagnostic state while using monotonic timestamps for timeout decisions; reject the lazy UTC-anchor candidate because clean interleaved RPC workloads did not show a stable benefit
• document the remaining intentionally external clocks and add deterministic before/equality/after, cleanup, race, and provider-isolation coverage

Validation

• dotnet format whitespace Sharplink.slnx --no-restore --verify-no-changes
• Release solution build: 0 warnings, 0 errors
• Unit 764/764; Generator 124/124; LoadTest 8/8; StreamLoad 21/21; Integration 275/275
• generated-assembly dependency verification and independent-process shared-memory NativeAOT smoke
• clean-commit pack, package identity/symbol/dependency verification, package consumer smoke, Oneway demo, and shared-memory load smoke
• 120-second shared-memory Chaos: 787,320 successful calls, 170,838 injected failures, 11 restarts, 0 unexpected/client/server/unobserved errors
• retained MarkActive: 32.65 ns; retained MarkActive plus LastActive: 32.97 ns; zero managed allocation and equivalent to the exact baseline

Closes #77
Closes #94