Closes ADR 0008. Architectural changes:
- gRPC RuntimeService as primary protocol
- Python + TypeScript SDKs (kakeya, @kakeya/runtime)
- HTTP shim deprecated, single-shot-session wrapper
- Linux CI gate is verifier-independent boundary (no test doubles)
- Mac M4 self-hosted integration gate via needs-mac-m4 label

GA gate evidence:
- INV-3 byte-exact (PR-E1, integration suite)
- Prefill bounded: 9ms drift over 14400s on Mac M4 (PR-E1b)
- KV bounded: architecturally + empirically (PR-E1c)
- 80 integration tests passing on Mac M4 (post-D2/E2)

Compared to v0.2.0:
- 4400× latency-drift improvement on long sessions
- 8.3× turn throughput at the same workload
- Zero test doubles in Linux CI gate (1148 stmts, 100% coverage)