Rust SDK for DSH(Deepseek Harness)

Key features

• HarnessClient (low-level)spawns the runtime process, owns the stdio transport, speaks the JSON-RPC 2.0 wire protocol, and fans notifications out to subscriptions.
• cargo test — wire-protocol, lifecycle, and Session::run semantics suites against a scripted fake runtime (no real runtime needed).
• Exposes LaunchSpec, ClientTimeouts, and NotificationSubscription.
• DeepSeekHarness / Session (high-level): the Python-parity owned-run API on top of HarnessClient.
• Input accepts either plain text (Input::Text) or raw content blocks (Input::Blocks), mirroring Python's normalize_input.