dotnet-server: Rich Interactions runtime + choices kind (AskUserQuestion)

[brentrager]

Problem

Wave 2 of the polyglot Rich Interactions effort. The Rust reference merged (#475); the .NET (C#) server — Brent's tsx-dev-agent host — needs the same runtime + the choices kind. Until now the C# server had only the write-confirmation park/resume, not the generalized kind-agnostic interaction framework.

Solution

Mirror the Rust reference (interaction.rs + tools/interaction.rs + choices.rs + the server wiring) idiomatically in C#, reusing the existing ConfirmationRegistry park/resume pattern generalized.

Framework (dotnet/server/src/Interactions.cs)

• IInteractionKind / InteractionCatalog — the extension seam + kind catalog (default = choices).
• InteractionParkRegistry — session-keyed park store with peek vs resolve (an invalid submit re-prompts without consuming the park), the interaction analog of ConfirmationRegistry.
• RequestInteractionTool / SubmitInteractionTool (both AIFunction) — the per-kind request_<kind> raise tool (rich → park + interaction_required; fallback → conversational directive) and the generic submit_interaction fallback tool.

The choices kind (dotnet/server/src/ChoicesKind.cs, mirrors choices.rs)

• request_choices (1–4 questions, header ≤12 unique, 2–4 options, optional multiSelect), ChoicesValidator.Validate (all-answered; labels ∈ options; single = one label XOR other, multi = ≥1; blank other dropped; one-pass errors), fallback directive, capability id choice_chips.

Server wiring

• ProtocolEvents.InteractionRequired / InteractionInvalid — double-nested data.data envelopes matching spec/events/*.schema.json.
• submit_interaction dispatch in FrameDispatcher (validate → resume; invalid → retryable interaction_invalid, turn stays parked; decline path; INTERACTION_MISMATCH / NO_PENDING_INTERACTION; ownership-scoped).
• Per-connection supports capture at create_conversation_session drives the rich-vs-fallback branch; teardown/cancel unpark the park.
• The catalog is a DI-provided capability (AddSmoothOperatorServer registers InteractionCatalog.Default), so direct FrameDispatcher construction stays unchanged.

Verification

• Validator unit tests (ChoicesInteractionTests, 14): ported from choices.rs's #[cfg(test)] block, plus the shared choices_spec / choices_values / choices_payload conformance fixtures fed through the C# validator (canonical payload must equal the fixture).
• Park/resume integration tests (SubmitInteractionTests, 5) over the real WS harness: raise → interaction_required → submit_interaction → resume; invalid → stays parked → resubmit; decline; text-only fallback (no capability → no card, conversational directive); no-pending error.
• Full solution Release build + dotnet test: server unit 371, integration 90, conformance 36 (1 skipped), host 6 — all green. spec/interactions/choices.schema.json conformance already validated by the shared ConformanceTests.

🤖 Generated with Claude Code

https://claude.ai/code/session_01YbN45JeWDbcjvFqGJvmVD3

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Latest commit: 0ffc075

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Name	Type
@smooai/smooth-operator	Patch
@smooai/smooth-operator-web-chat-example	Patch

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