[Feature] Support C# SDK spec-driven model generation workflow

[hittyt]

Why do you need it?

Is your feature request related to a problem? Please describe in details

The current C# SDKs (sdks/sandbox/csharp and sdks/code-interpreter/csharp) are manually maintained and do not have a spec-driven model generation workflow, unlike Python/JavaScript/Kotlin SDKs.

This creates several practical issues:

• Spec drift risk: when specs/sandbox-lifecycle.yml or specs/execd-api.yaml changes (e.g. new fields like ossfs, subPath, or schema updates), C# models may lag behind.
• Higher maintenance cost: developers must manually update multiple model/adaptor files and tests.
• Inconsistent multi-language experience: the same API feature may appear quickly in some SDKs but later in C#.
• No CI guardrail for generation freshness: there is currently no “generate + diff check” step for C# in CI, so stale models can slip into PRs.

How could it be?

A clear and concise description of what you want to happen. You can explain more about input of the feature, and output of it.

Introduce a spec-based model generation pipeline for C# SDKs and integrate it into local workflows + CI.

Proposed scope (v1)

1. Generator entrypoint

   • Add generation script/command for C# (e.g. under sdks/sandbox/csharp/scripts/ and sdks/code-interpreter/csharp/scripts/).
   • Inputs:
     • specs/sandbox-lifecycle.yml
     • specs/execd-api.yaml
   • Output:
     • generated API/model layer in deterministic paths (or generated intermediate + mapped domain models).

2. Repository workflow integration

   • Add documented commands in C# SDK README/CONTRIBUTING:
     • generate-api
     • verify-generated
   • Ensure generated artifacts are reproducible and stable.

3. CI enforcement

   • In .github/workflows/sdk-unit-tests.yml (or a dedicated workflow), add:
     • generation step
     • git diff --exit-code check for generated files
   • Fail PR when specs changed but C# generated outputs are not updated.

4. Compatibility approach

   • Keep current public SDK ergonomics.
   • If needed, use a thin adapter/converter layer between generated types and current domain types to avoid breaking API ergonomics.

Acceptance criteria

• Running the documented generation command updates C# generated artifacts from latest specs.
• CI fails when generated outputs are stale.
• C# SDK models include latest spec fields (including OSSFS-related fields where applicable).
• Existing C# unit tests continue to pass.

Other related information

Add any other context or screenshots about the feature request here.

• Current CI for C# mainly runs tests and packaging, but does not verify generated freshness.
• Related workflows:
  • .github/workflows/sdk-unit-tests.yml
  • .github/workflows/publish-csharp-sdks.yml
• Related specs:
  • specs/sandbox-lifecycle.yml
  • specs/execd-api.yaml
• Goal of this issue is automation and consistency; no urgent runtime behavior change is required in this PR.

[ninan-nn]

Working on it.