docs: polyglot engines — install + usage for all 5 languages

[brentrager]

Problem

The repo ships the agent engine in five languages (Rust, TypeScript, Python, Go, C#/.NET), all now published and consumable, but there was no single page telling a consumer how to install each one and write a first agent. The README's repository-layout table still lists TS/Python/C# as "Planned."

Solution

Adds docs/Polyglot-Engines.md:

• What it is + topology — smooth-operator-core is the polyglot ENGINE library (in-process agentic loop, the "LangGraph" analog); the separate smooth-operator repo is the SYSTEM/service that consumes it (the "Onyx" analog). Parity is enforced by behavior via a shared eval suite, not identical type shapes.
• Feature surface — one list of what every engine supports at parity (loop, RAG, memory, compaction, cost/budget, checkpointing, rerank, sub-agents, cast, human-gate, thread, LlmProvider seam + mock, deferred tools + tool_search, workflow graph, parallel tool calls, retry/backoff, streaming).
• Per language — install command + package name/version + a minimal "hello agent" (mock provider, one turn) using the actual API.
• Streaming subsection — the TS runStream StreamEvent tagged union.
• Links each engine directory and notes the eval suite enforces parity.
• One-line pointer from the README repository-layout section.

Verification

Every example was checked against the real engine source / tests so the type and method names are accurate:

• Rust — rust/smooth-operator-core/src/agent.rs (Agent, AgentConfig::new, with_llm_provider, run → Conversation), llm_provider.rs (MockLlmClient, push_text, Clone), lib.rs exports (mock is under llm_provider::), providers.rs/llm.rs (LlmConfig::openrouter), conversation.rs (last_assistant_content).
• TypeScript — typescript/core/src/index.ts exports, agent.ts (SmoothAgent ctor takes ChatClientLike + AgentOptions, run → AgentRunResponse.text, runStream → StreamEvent union), llmProvider.ts (MockLlmProvider implements ChatClientLike, pushText).
• Python — python/core/src/smooth_operator_core/__init__.py, agent.py (SmoothAgent(chat_client, options), async run → result.text, AgentOptions dataclass all-default), llm_provider.py (MockLlmProvider.push_text); matched against python/core/tests/test_agent.py.
• Go — go/core/agent.go (NewSmoothAgent, Run(ctx, msg, history) → AgentRunResponse.Text, AgentOptions struct), llm_provider.go (NewMockLlmProvider().PushText); matched against go/core/agent_test.go. Import path …/go/core (package core).
• C# — dotnet/core/src/SmoothAgent.cs (RunAsync, RunStreamingAsync), LlmProvider.cs (MockLlmProvider : IChatClient, PushText), AgentOptions.cs, AgentRunResponse.cs (Text).

Markdown matches the repo's existing prose/code style (long prose lines and gofmt tabs in the Go block; the repo has no markdownlint config and its own README runs lines >80 chars).

🤖 Generated with Claude Code

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